If y varies directly as x, there exists some variation constant k such that

y = k*x

Dividing both sides by x, we have an expression for k.

Y/x = k

You have been given values of y and x, so this is easily computed.

36/9 = k = 4

y = k*x

Dividing both sides by x, we have an expression for k.

Y/x = k

You have been given values of y and x, so this is easily computed.

36/9 = k = 4