(3h-2m)(2h+m) multiple

If you want to multiply 2 binomials, take each term in the first set of parentheses and multiply it to every term in the second set of parentheses:
3h*(2h+m) = 3h^2+3hm
-2m*(2h+m) = -4hm-2m^2
Combine like terms: (3hm-4hm)
3h^2-hm-2m^2