Pete began solving the system {x+3y=132x-y=-2 by rewriting the system as {x+3y=136x-3y=-6.

Which property justifies this step?

a. addition property of equality

b. subtraction property of equality

c. substitution property of equality

d. multiplication property of equality

The answer would be multiplication property of equality. For this property, it states that when you multiply one side of the equation, the other should be multiplied as with the same factor for the equation to be still the same. For this case 3 was multiplied to both.