Let $f(x) = \frac{7x+6}5$ and g$(x) = 10x+10$. Determine $(-10f+5g)(-4)$

Question

I would like to know how to approach this in the first place. I would think just subbing the function equations in for $f(x)$ and $g(x)$ would work, but all the answers are integers with no x in them. Any help would be greatly appreciated

Let $f(x) = \frac{7x+6}5$ and $g(x) = 10x+10$.

Determine $(-10f+5g)(-4)$

Answer 1

I guess the difficulty that you face is how to evaluate $(-10f+5g)$

Note that $$(-10f+5g)(x)=-10f(x)+5g(x)$$

Evaluate it by letting $x= - 4$.

Answer 2

$$(-10f+5g)(-4)=-10\cdot\frac{7(-4)+6}{5}+5\cdot(10(-4)+10)=-106$$