The equation is .

Apply addition property of equality: Add 5 to each side.

                       (Apply additive inverse property: )

                             (Apply additive identity property: )

r = 13                                 (Add:  5 + 8 = 13)

Check:

To check the solution, substitute r = 13 in original equation.

8 = 8                                    (Subtract: 13 – 5= 8)

The statement is true.

To graph the solution on the number line:

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• Draw the number line.
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• Mark a dot at 13 on the number line. 
\

The value of r = 13.