Answer:
r = 7
Explanation:
Isolate the variable, r. Note the equal sign, what you do to one side, you do to the other. Add 3 to both sides of the equation:
r - 3 = 4
r - 3 (+3) = 4 (+3)
r = 4 + 3
Simplify. Combine like terms:
r = 4 + 3
r = 7
r = 7 is your answer.
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