Solve using the addition property of equality. Don't forget to perform a check.
x - 9 = 21
To solve for x using the addition property of equality, we need to isolate x on one side of the equation.
Given: x - 9 = 21
Add 9 to both sides of the equation:
x - 9 + 9 = 21 + 9
x = 30
Now, let's perform a check by substituting x = 30 back into the original equation:
30 - 9 = 21
21 = 21
Since the equation is true after substituting x back in, the solution x = 30 is correct.