Answer:
7
Explanation:
is a difference of squares.
When factoring a difference of squares, you can use this formula
.
So
can be factored as
.
So back to the problem:
Rewriting with a factored left hand side:

We are given x-y=4 so rewriting again with this substitution:

Dividing both sides by 4:

So we have x+y equals 14.
We are asked to find the average of x and y which is (x+y)/2.
So since x+y=14 , then (x+y)/2=14/2=7.