Use Substitution to solve 3d + 8i = 64 and 9d + 7i = 107

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Use the substitution method to solve:

3d + 8i = 64

9d + 7i = 107

Check Format

Equation 1 is in the correct format.

Check Format

Equation 2 is in the correct format.

Rearrange Equation 2 to solve for d:

9d + 7i = 107

Subtract 7i from both sides to isolate d:

9d + 7i - 7i = 107 - 7i

9d = 107 - 7i

Now divide by 9:

Revised Equation 2:

Plug Revised Equation 2 value into d:

3(d) + 8i = 64

3 * ((107 - 7i)/9) + 8i = 64

((321 - 21i)/9) + 8i = 64

Multiply equation 1 through by 9

9 * (((321 - 21i)/9) + 8i = 64)

9 * (((321 - 21i)/9) + 8i = 64)

321 - 21i + 72i = 576

Group like terms:

-21i + 72i = 576 - 321

51i = 255

Divide each side by 51

i = 5

Plug this answer into Equation 1

3d + 8(5) = 64

3d + 40 = 64

3d = 64 - 40

3d = 24

Divide each side by 3

d = 8

Test Your Knowledge?

1. What are the 3 methods to solve a system of 2 equations?
2. With the elimination method, what are you trying to eliminate?

Common Core State Standards In This Lesson

CCSS.MATH.CONTENT.8.EE.C.8,CCSS.MATH.CONTENT.8.EE.C.8.B

What is the Answer?

d = 8 and i = 5

How does the Simultaneous Equations Calculator work?

Free Simultaneous Equations Calculator - Solves a system of simultaneous equations with 2 unknowns using the following 3 methods:
1) Substitution Method (Direct Substitution)
2) Elimination Method
3) Cramers Method or Cramers Rule Pick any 3 of the methods to solve the systems of equations 2 equations 2 unknowns
This calculator has 2 inputs.

What 1 formula is used for the Simultaneous Equations Calculator?

Δ = a * e - b * d

What 7 concepts are covered in the Simultaneous Equations Calculator?

cramers rule

an explicit formula for the solution of a system of linear equations with as many equations as unknowns

eliminate

to remove, to get rid of or put an end to

equation

a statement declaring two mathematical expressions are equal

simultaneous equations

two or more algebraic equations that share variables

substitute

to put in the place of another. To replace one value with another

unknown

a number or value we do not know

variable

Alphabetic character representing a number

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