Step-by-step explanation:
The initial expression is:
3x - x + 5x + 12
The terms 3x, -x and 5x are like terms. So, we can simplify the expression using the distributive property as:
3x - x + 5x + 12
(3 - 1 + 5 )x + 12
7x + 12
Therefore, the simplified expression is: 7x + 12
Answer: 7x + 12