Answer:
r = 9
Step-by-step explanation:
These are vertical angles, therefore, the measurements is the same. Set the two measurements equal to each other:
7r - 5 = 6r + 4
Isolate the variable, r. Note the equal sign, what you do to one side, you do to the other. Add 5 and subtract 6r from both sides of the equation:
7r (-6r) - 5 (+5) = 6r (-6r) + 4 (+5)
7r - 6r = 4 + 5
Simplify:
7r - 6r = 4 + 5
r = 9
9 is your value for r.
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