Answer:
15
Step-by-step explanation:
because it the 0 that need to subtract
The missing reason in step 8 is the substitution property.
<h3>What is substitution property?</h3>
It should be noted that according to substitution property, if x = y, then x can be substituted for y in any equation.
When a variable is equal to another variable, then the variables can be interchangeable.
In this case, the missing reason in step 8 is the substitution property.
Learn more about substitution property on:
brainly.com/question/12289041
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Are there any answer choices?
7a+7b+77
I I hope this helps you