Question

If y varies directly as x, and y is 18 when x is 5, which expression can be used to find the value of y when x is 11?

y=5/18(11)

y=18/5(11)

y=(18)(5)/11

y=11/(18)(5)

Answer 1

If y varies directly as x, then y=kx.

Since y=4, when x=-2, plug it into the formula above, and you have
y=kx
4=k(-2)

Solve for k, k=-2

Now, y = -2x, so if x=30

Answer 2

find the equation and get your answer