Answer:
To simplify the expression x - 15 + 2x + 6, you can combine like terms. Here are the steps to do that:
Group the x terms and the constant terms separately:
(x + 2x) + (-15 + 6)
Simplify the terms inside the parentheses:
3x - 9
So the simplified expression is 3x - 9.
Therefore, x - 15 + 2x + 6 equals 3x - 9.