IXL - Solve a system of equations using substitution (Algebra 1 practice)

Solve using substitution.

^–7x − 8y = 10

x = ^–6

(, )

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question

Solve using substitution.

5x + 7y = ^–6

y = ^–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:

5x + 7y = ^–6

y = ^–8

Step 1: Isolate a variable.

The variable y 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 y = ^–8 into the other equation, 5x + 7y = ^–6, and find the value of x.

5x + 7y

^–6

Plug in y = ^–8

5x + 7(^–8)

^–6

Plug in y = ^–8

Multiply

5x − 56

^–6

Multiply

Add 56 to both sides

Divide both sides by 5

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 y = ^–8, so it is not necessary to plug in and solve for y.

Step 4: State the solution.

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

Looking for more? Try these:

Lesson: Systems of equations

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C.12Solve linear equations with variables on both sides

O.1Is (x, y) a solution to the system of equations?

Lesson: Systems of equations

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