The heights of a maple tree and a cherry tree have a ratio of 5: 2. if the maple tree grew 20 cm and 20 cm was cut off the top of the cherry tree, the ratio of their heights would be 3: 1. how much taller is the maple tree than the cherry tree?

Let x be the heights of a maple tree and y be the height of the cherry tree.
We know: 

The new ratio is obtained like this:
.
From the above equation we get .
then 
Solving the above equation for y we get: 
So 
So the first tree is (400-160=240) more taller than cherry tree.