$$ \begin{aligned} \frac{1}{3}(9k+12) &= 15&& \text{simplify left side} \\[1 em]\frac{9k+12}{3} &= 15&& \text{multiply ALL terms by } \color{blue}{ 3 }. \\[1 em]3 \cdot \frac{9k+12}{3} &= 3\cdot15&& \text{cancel out the denominators} \\[1 em]9k+12 &= 45&& \text{ move 12 to the right } \\[1 em]9k &= 45-12&& \\[1 em]9k &= 33&& \text{ divide both sides by $ 9 $ } \\[1 em]k &= \frac{33}{9}&& \\[1 em]k &= \frac{11}{3}&& \\[1 em] \end{aligned} $$

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