Algebra Using Addition

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

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

Example:

For any variables, X, Y and Z; if {X=Y}, then {X+Z = Y+Z}

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Note that "Z" can be a negative or a positive number.

Example:

(1+Z = 1+Z)

or

(1+(-Z) = 1+(-Z)

(1+98=1+98)

or

(1+(-98)=1+(-98))

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

Example:

(2=2)

If you add Y to one side

(2+Y=2),

then you

    must
add Y

to the other side too.

(2+Y=2+Y).

Example 1

 Solve (Y+18= -7)

(Y+18=-7)Add -18 to each side.
( Y+18+(-18)=-7+(-18) )
(Y+0=-25)
(Y=-25)

THEN

CHECK YOUR WORK

(A+18=-7)
(-25+18=-7)
(-7=-7)
If the last line equals out, the equation has been solved correctly.

Example 2
Your ship is flying above Planet X. It decreased 153 miles to 438 miles above the surface. How high above Planet X was it to start with?

FIND

Within the problem, find out what is being asked. The problem asked how high your ship originally was. Then define a variable for the missing value, and ours will be X.

The answer to the problem is the space ship's current altitude.

PLAN

Create an equation for the problem. The equation is X-153=438, where X equals the original location.

SOLVE

Solve the Equation.
Since the ship ascended to 438 meters and then descended 285 meters, the equation is:
(X-153=438)
Add 153 to both sides of the equation
(X-153+153=438+153)
The answer is X=591, so the ship was 591 miles above the surface.

Subtraction