Given f(x)=2x+5 and g(x)=8x+2
then what is (f−g)(−9)) ?

Subtract these functions:

(f-g)(x) = (2x+5) - (8x+2) = 2x+5 - 8x -2 = -6x + 3

Then substitute -9 for "x" :

(f-g)(-9) = (-6) * (-9) + 3 = 54 + 3 = 57

:)

Where's the rest of the