a)
y varies directly as x, that means y α x
y = kx, where k = constant of proportionality.
y = kx, recall y = 9, x= 18
y = kx
9 = k*18
18k =9
k = 9/18 = 0.5
y = kx, substitute k = 0.5
y = 0.5x
b)
x = 5, y = ?
y = 0.5x
y = 0.5*5
y = 2.5
Hope this helps.
