− (7 − x) + 5 = x + 7

Expand out the brackets:

−7 + x + 5 = x + 7

Subtract x from both sides:

`-7+5=7`

Simplify the left hand side:

`-2 = 7` ????

This is not possible, so we conclude that there are no possible values for x.

[There was a hint in the question that something funny may be going on. Always be aware that an equation may not have solutions. Also, there are times when you get solutions that cannot possibly work, so you have to discount them. We find such examples later in Equations with Radicals.]