Question: x - 3 = 9

Add 3 to each side of the equation

x = 12.

What property justifies this?

Answer: Addition Property of Equality

Question: x + 3 = 9

Subtract 3 from each side of the equation.

x = 6

What property justifies this?

Answer: Subtraction Property of Equality

Question: 0.5x = 4

Multiply both sides by 2

x = 8

What property justifies this?

Answer: Multiplication Property of Equality

Question: 3x = 12

Divide both sides of the equation by 3

x = 4

What property justifies this?

Answer: Division Property of Equality

Question: 2x + 7 = y. Also, x = 3.

Therefore, 2(3) +7 = y

What property justifies this?

Answer: Substitution Property of Equality