Combine any like terms in the expression. If there are no like terms, rewrite the expression.

To combine the like terms in the expression \( 3x + 2x - x - x \):

1. Combine \( 3x \) and \( 2x \): \[ 3x + 2x = 5x \]

2. Now, combine the remaining terms \( -x - x \): \[ -x - x = -2x \]

3. Now, combine \( 5x \) and \( -2x \): \[ 5x - 2x = 3x \]

So, the simplified expression is: \[ \boxed{3x} \]