Answer:
y = 36
Explanation:
given y varies directly with x then the equation relating them is
y = kx ← k is the constant of variation
to find k use the condition when x = 5 , y = 15
15 = 5k ( divide both sides by 5 )
3 = k
y = 3x ← equation of variation
when x = 12 , then
y = 3 × 12 = 36