## Algebra 1: Common Core (15th Edition)

$x=-2$ $y=5$
For the equation below to be true, the corresponding numbers in the first two matrices added together must equal the corresponding number in the final matrix. Lets use: $x+4y=18$ $2x+y=1$ Solve for y with the second equation: $y=1-2x$ Substitute the equation for y into the first equation: $x+4(1-2x) = 18$ Then solve for x: $x+4(1-2x) = 18$ $x+4-8x=18$ $4-8x+x=18$ $4-7x=18$ $-7x=18-4$ $-7x=14$ $x=\frac{14}{-7} =-2$ Now substitute -2 in place of x in the second equation to find y: $y=1-2x$ $y=1-2(-2)$ $y= 1+4$ $y=5$