8.3 Solving Systems by Addition

S. Blaylock

Lakota West Freshman

2009-2010

Solve using the substitution method4x + 3y = 31

Y = 2x + 7

Another method for solving systems is the Addition Method.

x + y = 5

x – y = 1

This method is especially useful when both equations are in standard form.

Solve each of the following using the addition method.

x + y = 5

x – y = 1

Solve using the addition method.

3x – 3y = 6

3x + 3y = 0

Use the Multiplication Property of Equality, then solve using the addition method.

2x + 3y = 8

x + 3y = 7

Use the Multiplication Property of Equality, then solve using the addition method.

3x – 6y = -6

5x – 3y = 14

Problem-Solving using the addition method.

The sum of two numbers is 56. The sum of one third of the first number and one fourth the second number is 16. Find the numbers.

Write the equations.

Use the addition method to find the first number.

Use the first number to find the second.

Answer the question.