If you’d like to see the world’s saddest math equation, just watch “World’s Best.” After being given a lighthearted “equation of me” homework assignment on the first day of school, 12-year-old Prem Patel (Manny Magnus) formulates the following: Prem = (mom + dad) x math + Jerome – dad.” A math whiz still reeling from the loss of his father, Prem (it rhymes with “name,” not that anyone ever pronounces it correctly) proves easy to root for as he navigates adolescence in “7 Days” director Roshan Sethi’s coming-of-age dramedy. But while the Disney+ original ultimately receives a passing grade, it doesn’t exactly ace the assignment the way its protagonist so often does. Prem’s ostensible nemesis as he prepares for the upcoming Mathlympics competition is fellow math genius Claire (Piper Wallace), who literally haunts his stress dreams and proudly declares that her family “doesn’t celebrate summer” after being asked how she spent the last three months, while his best friend is aspiring Tik Tok star Jerome (Max Malas). Then there’s his mother Priya (Punam Patel), who has spoken little of her deceased husband Suresh (Utkarsh Ambudkar) in the seven years since his passing. Parents just don’t understand, especially when they aren’t around. Well, about that… The film’s most charming sequence is a flashback in which Prem’s mother walks him through the night she met his father, both participating in and commenting on the events. She downplays her feelings for a former flame, insists she only went out on weekends (unless there was nothing to study for, that is) and does her utmost to maintain her maternal image while telling the story. After this origin-story explainer, in which Prem learns that his dearly departed dad was a talented freestyle rapper, his father appears and convinces the boy that he, too, should start rapping. For … reasons. A number of wish-fulfilling reveries in which father and son perform together – sometimes in front of an adoring crowd while wearing matching tracksuits, other times as though in a music video – follow, buffeted by lucid intervals in which Prem is thrust back to reality. As he begins to care less about algebra and more about spitting bars, his waking and dream selves begin to merge. This is much to his mother’s chagrin, not only because she finds the subject of Prem’s father too difficult to talk about most of the time but also because she’s a fellow math nerd who’d rather see him follow in her footsteps than his father’s. In their harshest exchange, she goes so far as to tell him that “this obsession with your father isn’t healthy.” You can probably guess how this tension is ultimately reconciled. And while it would be tempting to say that “World’s Best” is effective despite being predictable, it mostly isn’t. That the actual rapping isn’t especially good might be said to lend the film a certain level of realism, but mostly it just makes the many, many musical sequences feel like a chore. Which is odd, given that Ambudkar – who also co-wrote the screenplay, executive produced and collaborated on the music – is an accomplished rapper under the stage name UTK the INC and producer Thomas Kail won a Tony for directing “Hamilton.” (Ambudkar is no less familiar onscreen, having recently appeared in the likes of “Free Guy,” “Marry Me” and “Tick, Tick… Boom!”) He’s casually charming as the spritely paterfamilias who never bothers to explain exactly how he’s managed to appear in front of his initially disbelieving son, and the too-few scenes in which they simply hang out with each other are among the film’s best. Though very much aimed at the kiddos, “World’s Best” does throw the elder millennial parents who will be watching with their children: a “Dead Poets Society” reference here, a Doug E. Fresh cameo there. The rest of it, especially from the second act on, mostly consists of Prem’s imagined performances; it really is difficult to overstate how much of the movie takes place in its protagonist’s imagination. That isn’t a problem in and of itself, as many kids are prone to flights of fancy, but there’s surprisingly little real-world payoff to Prem’s daydreams. Despite Suresh’s oft-repeated mantra that “the world’s best never rest,” it’s hard not to wish that the movie itself would take more breaks and give father and son time to bond with one another.