Give kids a number & task them with coming up with as many different equations or ways to get to that number. Then, in whole class group, have students mark through any equation they write that others did too.
No points are received for equations that other individuals or teams wrote down. Only original equations ( ie. equations no one else wrote down) get a point. Do a few rounds to determine winner.
Allowing all to participate in this competition works out the high & low kids brains. Striking through duplicate equations pushes kids to invent new, more complex ones.
In more complex courses, give kids equations, bigger numbers, or complex variables that challenge that group. Students still have to come up with equations in competitive environment :)