Answer:
y = 0.4x
Explanation:
given that 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 y = 4 when x = 10 , then
4 = 10k ( divide both sides by 10 )
= k , that is
k = 0.4
y = 0.4x ← equation of variation