IXL - Solve a system of equations using substitution (Algebra 2 practice)

Solve using substitution.

3x + 2y = 17

x = 3

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Learn with an example

question

Solve using substitution.

8x − 7y = 6

x = ^–8

(, )

key idea

To solve using substitution, follow these four steps:

Step 1: Isolate a variable.

Step 2: Plug the result of Step 1 into the other equation and solve for one variable.

Step 3: Plug the result of Step 2 into one of the original equations and solve for the other variable.

Step 4: State the solution.

solution

Use substitution to solve the system of equations:

8x − 7y = 6

x = ^–8

Step 1: Isolate a variable.

The variable x is already isolated in the second equation.

Step 2: Plug the result of Step 1 into the other equation and solve for one variable.

Plug x = ^–8 into the other equation, 8x − 7y = 6, and find the value of y.

8x − 7y

Plug in x = ^–8

8(^–8) − 7y

Plug in x = ^–8

Multiply

^–64 − 7y

Multiply

Add 64 to both sides

^–7y

Add 64 to both sides

Divide both sides by ^–7

^–10

Divide both sides by ^–7

Step 3: Plug the result of Step 2 into one of the original equations and solve for the other variable.

The second equation already shows that x = ^–8, so it is not necessary to plug in and solve for x.

Step 4: State the solution.

Since x = ^–8 and y = ^–10, the solution is (^–8, ^–10).

Looking for more? Try these:

Lesson: Systems of equations

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B.1Solve linear equations

CC.1Evaluate a linear function

Lesson: Systems of equations

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