3-6-1 Variables on Both Sides of the Equation

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3-6-1 Variables on Both Sides of the Equation

x

When a one step equation is solved, essentially the constants are sorted to

one side of the equation and the variable to the other. x 

3 x

20

8

8

5 x

3 x 3x

2x

Think of this as “moving” the constant 8 to the other side of the equation.

“Move” terms involving variables the same way.

2 Choose the term containing the variable with the smaller coefficient.

This doesn’t matter now, but will make things easier in other

2 equations.

2 2 Now there is only a two step equation to solve.

10

2x

10

2

2 x

2

5

 x

To solve equations with variables on both sides of the equal sign, first distribute. 2 ( 3 x

8 )

5

7 x

Then combine like terms.

Move all the variables to the same side.

6

13 x x

16

21

5

9

 x

7

 x

6

8

9 x

Solve the two step equation.

9 x

4 x

21

6

Subtract or add, and then divide. 

21

21

Every step isn’t needed in every equation. 4 x

27

8

( 2

2

 x x )

8 x

8 x x

27

4

6 3

4

Practice: a) 5x - 8 = 7x + 3 b) 3d - 1 = 4d + 9 c) 7x + 4 = 5x - 8 d) 6 - 5c = 2 + 9c e)

2 x

3

7

4 x

8

2 x

7 f) 0.23x-7x+4=4x-0.6+4x-8 g) 4

2 x

8

 

2

3 x

2s - 8 = 3s + 9

3s - 9 = 2s +10

4s - 10 = s + 11

-11 + s = 4s + 12

4 2

3

 x

1 7

8

7 x

9

12x-(5-3x)=7-9(2-3x)

3 2

3 x

7

2 5

8 x

3 1

2

3

4 x

8

3

4

8 x

50X - 80 = 70X + 30

4L - 12 = 8 +5L

2K + 3 = 6K - 4

4x - 10 = 10x + 4

3

 s

5

12

16

7

 s

4

15

3 x

2 x

4

3 ( 2 x

8 )

4 x

5 x

8 ( 2 x

1 )

h) 5 t

3

2

7 t

12

3 t

2

 t

 i) 15

 

8

3 x

4 x

8

3

 x

  j)

 x  5

 9 x x k) l) m)

3 x  ( x x

23 x  ( x  )  x 

3 x   x   4  x   2

123

8

2 x

5

15 ( 3 x

5 )

23

5 x

2

5

 x

3

4

 x

 

3 1

3

 7

8

 3 x  2 x  7

8 n) o) p) q) r) s) t)

5

3 x

2

34 x

7

24 x

8

4

2 x

17 x

4

3 x

5

10 x   x  10

 x  2 

 x  x x x  x  x x

 d

7

  d

 

4 d

     d

 

4 d

8 t

  t

7

5 t 9 21

 

2 t

7

 

10 t

    x

8

   

3 x

9

  x

 

13 x

4 x

  

5 x

8

 z 8

  z 9

  z

3 b

  b

9

 

3 b

10

5

9 8 x

 

  x 5

2

7 x

5

9

  n

4

5

3 n

  n

  n

8

 

3 x

8

  

2(4 x

5)

(2

 x

2(3 - (4 y + 8)) - (9 -2(3 y + 5)) = (2 y - 8) - 8 - (5y ) - 9 y + 10

 f

  f

8

    f

9

 

5

 f

5

 

 f

7

  f

8

 

12

15

3-6-2 Proportion Problems

The proportions on this page require the algebra methods learned to solve.

Example:

2

9 x

8(2

16

 7 x x

7 x x

5

 x

8

5) 7(

40 7

40 14 x

7

2 x x

 2)

14

Cross multiply.

Then distribute.

Subtract to get the variables to the same side of the equation.

Solve the two step equation.

 40  40

9 x  54 x  6

Practice: a)

2 a

3

9

3 a

5

 8 2 x

3

 5

3 x

5

 8 m b)

2

3 a a

9

2

8

5 m m

 10

4

5  2 3

 10

7

2 9

5  f f

10

15 m

5

 4 c)

9 8 s  9

 1 5 s  10

3

4

 t t 

3

8

24

8

10 k k

 8 d)

6

8

5 y

8

 10 3

16

 w

 w

8

 5 u

45

 8

5 u

3

 10

Remember to solve proportion problems, cross multiply, and then solve.

Examples: x

8

7

3

4

2

5 x

5 x

100

1

4

 x

7

24 100

2 x

5

5 x

1

4 x

28

24 200 x

25 x

5

28

28

4 x

52

175 x

5 x

1

35 x

4 x

4

13

52

4

Practice: a) x

4

5

 b) x

6

2

3

8 c)

2 x

9

 4 1

3 d)

3 x

5

5 x

6

2

3 x

5

5

8

2 x

3 x

5

8

( x x

7

3 3 8

)

3

2

( x x

 )

3

3 x

 x

3

 x

5

2

2

4

3

  x

5

9 x

6

4 x

20

4 x

4 x

5 x

6

6

20

6

5 x

26 x

5 1

5

2 x

8

7

5

3 x

2 x

6

7

3 x

5

8 x 

2

6

3  x  5 

5

6 

3 x

 x

2

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