Question

If f(x) varies directly with x, and f(x) = 12 when x = 8, write the direct linear variation equation.

Answer 1

f(x) varies directly with x.
f(x) = kx (k is the constant of proportionality)
if x = 8,
12 = 8 k
k = 12/8
k = 3/2
So the equation would be: 
f(x) = (3/2)x