15/35 = y/84
to find what value of y makes the proportion true, you actually just need to solve for y.
15/35 = y/84 ... first, multiply both sides by 84
(15*84)/35 = y
1260/35 = y
36 = y
so, these values are proportional when y = 36. you can check this by getting the decimal of both and seeing if they're equal:
(15/35) = 0.428
(36/84) = 0.428
