l Use Substitution to solve 10x - 15y = -70 and 3x - 5y = 15

Enter Equation 1

Enter Equation 2

    

Use the substitution method to solve:

10x - 15y = - 70

3x - 5y = 15

Check Format

Equation 1 is in the correct format.

Check Format

Equation 2 is in the correct format.

Rearrange Equation 2 to solve for x:

3x - 5y = 15

Add 5y to both sides to isolate x

3x - 5y + 5y = 15 + 5y

3x = 15 + 5y

Now divide both sides by 3:

3x
3
=
  
15 + 5y
3

Revised Equation 2:

x  =  15 + 5y
  3

Plug Revised Equation 2 value into x:

10(x) - 15y = -70

10 * ((15 + 5y)/3) - 15y = -70

((150 + 50y)/3) - 15y = -70

Multiply equation 1 through by 3

3 * (((150 + 50y)/3) - 15y = -70)

3 * (((150 + 50y)/3) - 15y = -70)

150 + 50y - 45y = -210

Group like terms:

50y - 45y = -210 - 150

5y = -360

Divide each side by 5

5y
5
=
  
-360
5

y  =  -360
  5

y = -72

Plug this answer into Equation 1

10x - 15(-72) = -70

10x + 1080 = -70

10x = -70 - 1080

10x = -1150

Divide each side by 10

10x
10
=
  
-1150
10

x  =  -1150
  10

x = -115

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