I believe the expression would be 7(g)+7
So if you do 3/5 it ends up equaling .6 you can convert that into a percent and it equals 60%
800+16x=720+21x
80+16x=21x
80=5x
X=16
So 16 hours :)
F(x) multiplied by g(x)
=
(x+12)(x-5)
Here you need to use the FOIL method (first, outside, inside, last)
Answer: x^2 - 5x + 12x - 60