Final answer:
Emily's first step in solving the equation is justified by the addition property of equality. This property states that if you add or subtract the same quantity from both sides of an equation, the equation remains true.
Step-by-step explanation:
Emily's first step in solving the equation:
x + 5 = 10
is to subtract 5 from both sides:
x + 5 - 5 = 10 - 5
This step is justified by the addition property of equality.
This property states that if you add or subtract the same quantity from both sides of an equation, the equation remains true.