
Home > CAAC > Chapter 7 > Lesson 7.3.1 > Problem 7-87
7-87.
One way to solve this system of equations is by using the substitution method.
y = 2x − 3. Substitute y:
x − y = −4
x − (2x−3) = −4
Solve for x.
Distribute the left side.
x − 2x + 3 = −4
Combine like terms.
−x + 3 = −4
Subtract 3 on both sides.
−x = −7
Use the solution you found for x and substitute it into either original equation and solve for y.
x = 7
y = 11
One way to solve this system of equations is by using the elimination method.
Multiply the top equation by 2.
2(y − x = − 2)
2y − 2x = −2
Add the two equations together by combining like terms.
2y − 2x = −4
−3y + 2x = 14
−y + 0 = 10
Solve for y.
When you find y, you can now subsitute the value into either original equation and solve for x.
Don't forget to check your solution!