Alberto uses the steps below to solve the equation.

1/2x - 3 = 7

Step 1: 1/2x - 3 + 3 = 7 + 3

Step 2: 1/2x + 0 = 10

Step 3: 1/2x = 10

Step 4: 2 (1/2) x = 2 (10)

Step 5: 1x = 20

Step 6: x = 20

Which justifies Step 6 of his work?

1. the addition property of equality

2. the identity property of addition

3. the multiplication property of equality

4. the identity property of multiplication

I think that would be option 4. (its common sense really!)

4. the identity property of multiplication

Step-by-step explanation:

From Step 5 to Step 6, the equation changes from 1x = 20 to x = 20. The only difference is that the x term is written as "x" instead of "1x."

The identity property of multiplication states that multiplying any number by 1 results in the original number; this means that 1x, multiplying x by 1, is the same as x.