Find the coefficient of y^4 in the expansion of (2y-5+3y^2)^6.
That's way too much multiplication to do by hand.
Fortunately, a useful tool has been provided for us, at
Per the "expand" tool on that page, the coefficient of y4 is 375.
But don't take my word for it, go there and see it for yourself. :-)
Would it be cheating, to use that website to avoid the drudgery of endless
multiplications? I do not consider it cheating to use any tool that has been
made available. It used to be slide rules, then calculators, now computers.