Question

Find the solution of the system of equations.-x + 3y = –153x + 3y = 21

Answer 1

Let:

$\begin{gathered} -x+3y=-15_{\text{ }}(1) \\ 3x+3y=21_{\text{ }}(2) \end{gathered}$

using elimination method:

$\begin{gathered} (1)-(2) \\ -x-3x+3y-3y=-15-21 \\ -4x=-36 \\ x=\frac{-36}{-4} \\ x=9 \end{gathered}$

replace the value of x into (1):

$\begin{gathered} -9+3y=-15 \\ 3y=-6 \\ y=-\frac{6}{3} \\ y=-2 \end{gathered}$