If 3^(x - y) = 27 and 3^(x + y) = 243, then x is equal to:

Explanation

3^(x - y) = 27 = 3^3, so x - y = 3.
3^(x + y) = 243 = 3^5, so x + y = 5.

Adding the equations gives 2x = 8, so x = 4.