SOLUTION: Using substitution to eliminate one of the variables. Show your work x+y=7 2x+3y=21

Question 741007: Using substitution to eliminate one of the variables. Show your work
x+y=7
2x+3y=21
Answer by TutorBecky(6) (Show Source): You can put this solution on YOUR website!
x+y=7
2x+3y=21
Work::
x + y = 7
-x -x
----------
y = -1x +7 :::: Just so you don't get confused x is the same as 1x
Plug the equation into the other for y
2x + 3 (1x +7 ) = 21 Distribute 3*1x+3*7
2x + 3x +21 = 21 Combine the same variables : 2x+3x
5x + 21 = 21
- 21 -21 Subtract 21 on both sides
------------
5x =0 Divide by 5 on both sides
-----
5 5
x = 0
Now to get y
x + y = 7
0 + y = 7
y =7

Now to check if your right;; Plug in your varibles
x+y=7
0+7= 7
7 = 7 Check!
------------
2(0) + 3 (7) = 21
0 +21 = 21
21=21 Check!
Hope i helped

RELATED QUESTIONS
Solve this system using the substitution method. -2x - y = -7 x + 7y = 10 Solve using... (answered by MathLover1)

Solve the system using substitution. Make sure to show your work for full credit. 2x (answered by rothauserc,Alan3354,amarjeeth123)

solve the system of equation using substitution to eliminate one variable. y=2x 3x+y=20 (answered by oberobic)

Solve the system of equations in 3 variables. 4x+2y-6z=-38 5x-4y+z=-18 x+3y+7z=38 (answered by Edwin McCravy)

how to eliminate variables by using the addition method?. 3x-4y+4z=7 x-y-2z=2... (answered by stanbon)

using the substitution method to solve the following system of equations. x + y = 3... (answered by richwmiller)

Solve the following system of equation using SUBSTITUTION to eliminate one variable. If... (answered by Maths68)

Solve this set of linear equations using the substitution method. Be sure to show all... (answered by MathLover1,MathTherapy)

please show me how to work these problems using the substitution method:... (answered by music974,math_kid)