f(x) 2x+1, g(x)=2x^2+x

determine (gf)(3)

ok so i dont know where to go since this is an online class

g(f(3)?

g(2(3)+1 = 7?

g(7)?

so confused someone please do this step by step i especially dont know how to do these when there are exponents like the 2x^2