Answer:
y = 4x
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 y = 16 when x = 4 , then
16 = 4k ( divide both sides by 4 )
4 = k
y = 4x ← equation of variation
When x = - 2 , then
y = 4 × - 2 = - 8