Step-by-step explanation:

x varies directly y

x /y = k--------( 1) k is constant

when x= 3 , y = 12

3 / 12 = k

1/ 4 = k

x / y = 1 / 4 ---------( 2 )

1) when y = 20 , x = ?

x / y = 1 / 4

x / 20 = 1 / 4

x = 1 / 4 × 20

x = 1 × 5

x = 5