Solving Linear Systems with Substitution - Definition & Examples

Which step is missing in solving the following system of equations by substitution? $$\begin{gather}3x - 2y = 7\\ 6x + y = 6\end{gather}$$

Solution: $$\begin{gather}x = \frac{7 + 2y}{3}\\ 6\left(\frac{7 + 2y}{3}\right) + y = 6\\ y = -\frac{8}{5}\end{gather}$$