Answer:
32
Step-by-step explanation:
Given that f(x) varies directly with x then the equation relating them is
f(x) = kx ← k is the constant of variation
To find k use the condition when x = 40, f(x) = 160
k = [tex]\frac{f(x)}{x}[/tex] = [tex]\frac{160}{40}[/tex] = 4, thus
f(x) = 4x ← equation of variation
When x = 8, then
f(x) = 4 × 8 = 32
