Elimination rules for method 2

Add equations

We can add them

Example

We can now solve 6x = 12 for x and get x = 2 (divide both sides by 6)

Elimination rules for method 2

Subtract equations

We can subtract them

Example

We can now solve 3s = 9 for s and get s = 3 (divide both sides by 3)

Elimination rules for method 2

Multiply by a number

We can multiply an equation by a number.

This process is known as scaling.

Example

Multiply 2b + 5r = 29 by 2 to get 4b + 10r = 58.

Typical problems require a combination of adding, subtracting and scaling of equations.

Practice

You can invent your own equations and then try to solve them.

Start with the answer, e.g., x = 2 and y = 5

Then make up two equations:

Problem

How did we get these equations?

Problem

Solve them.