If f (x) varies directly with x and f (x) = 2 when x = 10, then what is the value of f (x) when x = 40?

a. 8

b. 45

c. 200

d. 320

This is simple multiplication

do 2*4 and 10*4

so you get f (x) = 8 and x=40

if you wanna do it by doing division do

2=10

f (x) = 40

cross multiply then divide

so do 2*40 to get 80

then do 80/10 to get 8