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

Answer 1

Set it up as a direct variation equation y/x=k where k is the constant of variation. We have values for y and x and have to find k. 18/5=k, so k=3.6. Now plug in the other given y value and use that k value to find x: y/11=3.6 or
y/11=18/5, whichever your book or teacher prefers.