Answer:
subtraction property of equality
Explanation:
The equation in the question is incomplete, the complete equation is:
5 + x = 2
To solve this equation we have to use the subtraction property of equality, that is, if you subtract some number at both sides of the equal sign, the equation doesn't change. So:
5 + x - 5 = 2 - 5 (You must select a number which isolate x)
x = -3
And the answer is gotten.