\(\text{Area of a rectangle} = \text{base} \times \text{height}\). This means \(3r + 2\) will all be multiplied by 7. To show this in algebra, use a bracket for \(3r + 2\) to show that both terms are being multiplied by 7.

7 multiplied by \((3r + 2)\) can be written as \(7(3r + 2)\) as multiplication signs are not used in algebra.

\(\text{Area} = \text{base} \times \text{height}\)

Area = \(7(3r + 2)\)

\(56 = 7(3r + 2)\)

\(56 = 7 \times 3r + 7 \times 2\)

\(56 = 21r + 14\)

Isolate \(21r\) by subtracting 14 from both sides:

\(56 - 14 = 21r + 14 - 14\)

\(42 = 21r\)

Isolate \(r\) by dividing both sides by 21:

\(42 \div 21 = 21r \div 21\)

\(2 = r\)

Check that this answer is correct by substituting \(r = 2\) into the original equation.

\(7(3r + 2) = 7 \times (3 \times 2 + 2) = 7 \times (6 + 2) = 7 \times 8 = 56\)

The equation balances, so \(r = 2\) is the correct answer.