Question

If y varies directly as x, and y=21 when x=9, find x when y=52.5

Answer 1

21_____9
52.5_____x

X:52.5 * 9 / 22.5
X: 472.5/21
X: 22.5

Answer 2

When y=21 and x=9
21/9
which means that to go from x to y, you multiply x by 2.33
2.33x=y

2.33x=52.5
divide both sides by 2.33
x=22.53 (when rounded) 

so when y=52.5, x=22.53