What do you mean
Could you please insert an equation or a problem
I got 11.5 lol I don’t really know why
Since you have y alone on one side of the equation......
Use substitution and plug in 1/2x-4 for y in the other equation.
Distribute
Combine like terms
Add 8 to both sides
Divide by 4
and 
Plug this value in for x
Simplify
Multiply everything by 8 and simplify
Divide.....
Your answers are:
F(x) = 8 - 10x
g(x) = 5x + 4
Finding (fg)(-2).
First let us find fg(x), this is the same as f(g(x))
f(g(x))
f(5x + 4)
Recall, f(x) = 8 - 10x, therefore f(5x + 4) would be such that anywhere we see x in the f(x), we replace it with 5x + 4
f(x) = 8 - 10x
f(5x +4) = 8 - 10(5x + 4)
= 8 - 50x - 40
= -50x + 8 - 40
= -50x - 32
f(g(x)) = fg(x) = -50x - 32
fg(-2) = -50*(-2) - 32 = 100 - 32 = 68
Therefore fg(-2) = 68
I hope this helped.
