Question

Please solve these systems of equations by substitution.

1. x+y=7
x+2y=11

2. x+y=22
x+2y=48

3. x+y=45
x+2y=36

Answer 1

1. x=3 and y=4

2. x=−4 and y=26

3. x=54 and y=−9

Explanation:

1. x+y=7;x+2y=11

Step: Solvex+y=7for x:

x+y+−y=7+−y(Add -y to both sides)

x=−y+7

Step: Substitute −y+7 for x in x+2y=11:

x+2y=11

−y+7+2y=11

y+7=11(Simplify both sides of the equation)

y+7+−7=11+−7(Add -7 to both sides)

y=4

Step: Substitute 4 for y in x=−y+7:

x=−y+7

x=−4+7

x=3(Simplify both sides of the equation)

2. x+y=22;x+2y=48

Step: Solve x+y=22 for x:

x+y+−y=22+−y(Add -y to both sides)

x=−y+22

Step: Substitute−y+22 for x in x+2y=48:

x+2y=48

−y+22+2y=48

y+22=48(Simplify both sides of the equation)

y+22+−22=48+−22(Add -22 to both sides)

y=26

Step: Substitute26 for y in x=−y+22:

x=−y+22

x=−26+22

x=−4(Simplify both sides of the equation)

3. x+y=45;x+2y=36

Step: Solve x+y=45 for x:

x+y+−y=45+−y(Add -y to both sides)

x=−y+45

Step: Substitute−y+45 for x in x+2y=36:

x+2y=36

−y+45+2y=36

y+45=36(Simplify both sides of the equation)

y+45+−45=36+−45(Add -45 to both sides)

y=−9

Step: Substitute−9 for y in x=−y+45:

x=−y+45

x=−(−9)+45

x=54(Simplify both sides of the equation)

I hope this helped!

Answer 2

Explanation:

x+ 2(7-x) = 11

x+14-2x = 11

-x = -3

x = 3

3+ y = 7

y = 4

x + 2(22-x) = 48

x + 44 -2x = 48

-x = 4

x = -4

-4 + y = 22

y = 26

y = 45-x

x + 2(45-x) = 36

x + 90 -2x = 36

-x = 54

x = -54

-54 + y = 45

y = 99