Answer:
f(-5) = 15
Step-by-step explanation:
f(x)=5x+40
plug in x as -5
f(-5) = 5(-5) + 40
multiply 5 by -5
-25+40
add -25 to 40
15
For this case we have the following linear function:

Rewriting we have:

We observe that the linear function has:
Positive slope and equal to 2.
Intersection with the axis y equal to 6.
Answer:
y = 2x + 6
See attached image
The expression for 8 times x is just 8x