Phatgirl356
7

# how is 3x-y=8 and x+2y=5 solved by combination (addition)?????

$\begin{Bmatrix}3x-y&=&8\\x+2y&=&5\end{matrix}$ Now we can multiply the first row by 2 and add to the second row. $\begin{Bmatrix}3x-y&=&8\\7x&=&21\end{matrix}$ them $\begin{Bmatrix}3x-y&=&8\\x&=&3\end{matrix}$ now we can replace the value in the first row. $\begin{Bmatrix}3*3-y&=&8\\x&=&3\end{matrix}$ $\begin{Bmatrix}-y&=&8-9\\x&=&3\end{matrix}$ $\boxed{\boxed{\begin{Bmatrix}y&=&1\\x&=&3\end{matrix}}}$