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Solving Equations with Addition and Subtraction
You can add or subtract the same number on each side of an equation and the
result is an equivalent equation
. Equivalent equations have the same solution.
Addition Property of Equality |
For any numbers a, b, and c, if a = b, then a + c = b +
c. |
Subtraction Property of Equality |
For any numbers a, b, and c, if a = b, then a - c = b -
c. |
Solving Equations |
To solve an equation
means to get the variable (with a coefficient of 1) by itself on one
side of the equation. You can do this by undoing what has been done to
the variable, using the properties of equality. |
Example
Solve .
Solution
The number has been subtracted from x. The opposite of subtracting is adding . Add to each side of the equation.
is an equivalent equation. Simplify to obtain x = 1.
Check: Is ? Yes. The solution is 1.
Solving Equations with Multiplication and Division
You can solve a multiplication or division equation by using the
multiplication and division properties of equality.
Multiplication Property of Equality |
For any numbers a, b, and c, if a = b, then ac = bc. |
Division Property of Equality |
For any numbers a, b, and c, with c 0, if a = b, then . |
Example
Solve 
Solution
Rewrite the mixed numbers as improper fractions.
Multiply each side by , the reciprocal
of the number that is multiplied by x.

Solving Multi-Step Equations
Solving Multi-Step Equations |
- Work backward to isolate the variable and solve the equation.
- Use subtraction to undo addition, and use addition to undo
subtraction.
- Use multiplication to undo division, and use division to undo
multiplication.
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Consecutive integers are integers in counting order, such as
-3, -2, and -1.
Example
Solve .
Solution
Multiply each side by 4 to eliminate the fraction.

Next, undo the subtraction by adding 3 to each side.
2x - 3 + 3 = 36 + 3
2x = 39
Last, undo the multiplication by dividing each side by 2.

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