Inverse version of 27 = 3x

Explanation:

One equation we could solve is

x/2.5 = 30/7.5

Note the x/2.5 has us dividing the vertical sides, while 30/7.5 is the same idea for the horizontal sides. The order is large over small. You could do small over large, but make sure you keep both sides consistent.

Solving for x leads to...

x/2.5 = 30/7.5

x*7.5 = 2.5*30

7.5x = 75

x = 75/7.5

x = 10  (choice A)

There are many other possible equations that lead to the same answer. One other possible equation is x/30 = 2.5/7.5

These proportions are possible due to the fact we have similar triangles.