The function f (x) varies directly with x, and f (x) = 12 when x=8

which answer is the direct linear equation?

a) f (x) = 8x

b) f (x) = 12x

c) f (x) = 2/3x

d) f (x) = 3/2x

The answer would be d.

You can solve this by changing it up a little, such as changing it to f • x = 12

you can then divide by 8, because x = 8.

You're then left with f = 12/8 or 3/2

multiply by x again on both sides, and voila, f (x) = 3/2x