Jika 3y - 15 = 6y - 21, maka nilai 7y - 22 adalah...

Pembahasan

$$ \begin{align} 3y - 15 &= 6y - 21 \\ 3y - 6y &= -21 + 15 \\ -3y &= -6 \\ y &= \frac{-6}{-3} \\ \color{red}{y} &= \color{red}{2} \\ \\ 7y - 22 &= 7(\color{red}{2}) - 22 \\ \color{red}{7y - 22} &= \color{red}{-8} \\ \end{align} $$