Symbol
Problem
Solve the following systems of linear equations in two variables using substitution method. $1. \begin{cases} 3x-3y=12 \\ 3x+y=8 \end{cases}$ $2$ $\begin{cases} x-4y=6 \\ 2x-8y=12 \end{cases}$ $3.$ $\begin{cases} x+y=51 \\ y=2x \end{cases}$ $4. \begin{cases} 2x+3y=-17 \\ x=y+4 \end{cases}$ $5. \begin{cases} 2x+2y=3 \\ 8x-3y=1 \end{cases}$