To solve for X, we need to first simplify the right side of the equation:

3/5 + (-2/3) = 3/5 - 2/3
To add or subtract fractions, we need to have a common denominator. The common denominator for 5 and 3 is 15.

3/5 = 9/15
-2/3 = -10/15

Now we can rewrite the equation as:

X/15 = 9/15 - 10/15

Now we can combine the fractions on the right side:

X/15 = -1/15

To solve for X, we need to multiply both sides by 15:

X = -1

Therefore, the solution to the equation X/15 = 3/5 + (-2/3) is X = -1.