Given:
-x + 9y = 36 .......(1)
3x + 3y = 42 ........(2)
The equations can be solved using elimination method.
Multiply equation (2) by 3.
[tex]9x+9y=126\ldots\ldots(3)[/tex]Now, subtract equation (1) from (3).
[tex]\begin{gathered} 9x+9y-(-x+9y)=126-36 \\ 9x+9y+x-9y=90 \\ 10x=90 \\ x=\frac{90}{10}=9 \end{gathered}[/tex]Put x=9 in equation (1) and solve for y.
[tex]\begin{gathered} -9+9y=36 \\ 9y=36+9 \\ 9y=45 \\ y=\frac{45}{9} \\ y=5 \end{gathered}[/tex]Therefore, x=9 and y=5.
