Answer:
See below.
Explanation:
We have:
Given:

Step 1: Combining Like Terms (on the right):

Step 2: Distributive Property (distribute the -5 on the left):
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Step 3: Addition Property of Equality (add 7r to both sides):

Step 4: Addition Property of Equality (add 15 to both sides):

Step 5: Division Property of Equality (divide both sides by 2):
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And we're done!