Answer:
y = 21
Explanation:
given y varies directly as x then the equation relating them is
y = kx ← k is the constant of variation
to find k use the condition y = 7 when x = 4 , then
7 = 4k ( divide both sides by 4 )
= k , that is
k = 1.75
y = 1.75x ← equation of variation
when x = 12 , then
y = 1.75 × 12 = 21