When you know your equation f(x) and they want you to find f(-4), it means that they want to know what f(x) is worth when x=-4
Therefore, you only need to plug in you x in the equation
f(x)=5x-2
f(-4)=5(-4)-2
=-20-2
=-22 (B)
The formula to get the circumference is 2πr, π being pi and r being your radius.
Your r is 0.9 since the radius is half the diameter.
2πr = 2 x 3.142 x 0.9
= 5.6556cm
≈ 5.7cm
5m = -8 + 3m
2m = -8
m = -4