# Thread: substitution by system of equations

1. ## substitution by system of equations

3y + x = -1
2x+6=-5y

2. Originally Posted by daniegirl
3y + x = -1
2x+6=-5y
1. Solve first equation for x to get x = -1-3y

2. Substitute that value for x into the second equation and solve for y:

2(-1-3y)+6=-5y
-2-6y+6=-5y
4 = y

3. Substitute y = 4 into first equation to solve for x:

3(4) + x = -1
12 + x = -1
x = -13