Algebra Using Subtraction

In this particular lesson, you will learn how to solve equations dealing with Subtraction. At the end of the lesson, there is an optional test. Good Luck!

For the first example, we will show you the Subtraction Property of Equality.

Example:

For any variables X, Y, or Z; if {X=Y}, then {X-Z = Y-Z}
Note that "Z" can be a negative or a positive number.

Example:

(1-34=1-34)or(1-(+57)=1-(+57))

An Equation is almost like a scale. When you subtract something from one side, you have to subtract it from the other side.

Example:

(8=8)
If you subtract 1 from one side
(8-1=8),
then you must subtract 1 from the other side too.
(8-1=8-1)=(7=7).

Example 1

Solve (X+18= -7)

(X+18=-7)Subtract 18 from each side.
(X+18-18)=(-7)-18) )
(X+0=-25)
(X=-25)

Example 2

Astronauts in training have to lift weights in order to get in shape. Your pilot lifted 150 at first when he started training. He worked toward a goal of lifting 260 pounds. How many more pounds did he need to lift to reach his goal?