Substitution Method - Step by Step

Solve this equation

4x + 6(2) = 36

Answer explanation

4x + 6(2) = 36

4x + 12 = 36

Subtract 12 from both sides

4x = 24

Divide both sides by 4
x = 6

Tags

CCSS.7.EE.B.4A

Solve this equation

10(2) + 5y = 35

Answer explanation

10(2) + 5y = 35

20 + 5y = 35

Subtract 20 from both sides

5y = 15

Divide both sides by 5

y = 3

Tags

CCSS.7.EE.B.4A

Solve the following equation

3x + 4(x + 3) = 47

Answer explanation

3x + 4(x + 3) = 47

Distribute first

3x + 4x + 12 = 47

Combine like terms

7x + 12 = 47

Subtract 12 from both sides

7x = 35
Divide both sides by 7

x=5

Tags

CCSS.8.EE.C.7B

Place the correct numbers in the boxes.

a

b

c

d

6

30

1

21

Tags

CCSS.7.EE.B.4A

What does it mean to substitute?

• To graph and find the intersection

• To replace the value of a variable with an equivalent expression

• To solve an equation

• To substitute an answer with another answer

Tags

CCSS.6.EE.A.2C

Which of the following shows a correct substitution for the following system?

x = 4 and -3x + 6y = 18

• -34 + 6y = 18

• -3(4) + 6(4) = 18

• -3x + 6(4) = 18

• -3(4) + 6y = 18

After substitution, what solution did you find?

-3(4) + 6y = 18

• y = 1

• y = 5

• x = 1

• x = 5

Answer explanation

-3(4) + 6y = 18

-12 + 6y = 18

+12 +12

6y = 30

6 6

y=5

Using what you just found, find the solution to the following system.

x = 4 and -3x + 6y = 18

• (4, 3)
• (4, 5)
• (4, 1)

• (5, 4)

Tags

CCSS.HSA.REI.C.9

Which shows a correct substitution for the following system?

x = 3y - 2 and 2x - 5y = 2

• (3y-2) - 5y = 2

• 2(3y - 2) - 5y = 2

• 2x - (3y - 2) = 2

• 2x - 5(3y - 2) = 2

Answer explanation

Note, after you substitute, you should only see one type of variable. Either only x's or y's should be left in your equation.

Tags

CCSS.8.EE.C.8B

CCSS.HSA.REI.C.6

Solve the rest of the equation

2(3y - 2) - 5y = 2

Answer explanation

2(3y - 2) - 5y = 2

Distribute first

6y - 4 - 5y = 2

Combine like terms

1y - 4 = 2

• +4 +4

• 1y = 6

• y=6

Tags

CCSS.8.EE.C.7B