How do i answer this question

Combine like terms on the right side of the equal sign:

7 - 3x = - 3x + 7

You can rearrange the right side to be:

7 - 3x = 7 - 3x

Because are the same thing, your answer ends up being all real numbers or infinitely many solutions. This means whatever number you plug in for the x-variable, the two sides will always be equal to each other.