Answer:
x = - 6
Step-by-step explanation:
Given that 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 = - 9 when x = 3, thus
k = [tex]\frac{y}{x}[/tex] = [tex]\frac{-9}{3}[/tex] = - 3
y = - 3x ← equation of variation
When y = 18, then
18 = - 3x ( divide both sides by - 3 )
x = - 6
