Question 1201541
The average would be represented by (x+y)/2.  This is equal to 3y.  Then, their ages in 7 years would be x + 7 and y + 7.  This sum is greater than the difference of their ages by 20 years.  You don’t need to use a >.  By adding the 20 to the difference, that is showing that the sum would be greater than the difference by 20.

*[illustration Age_word_problem]