OPEN SENTENCES INVOLVING ADDITION AND SUBTRACTION

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An open sentence can be either true or false depending on what values are used. The value we don’t know is called a variable (also called an unknown). Solving means finding a value for the variable that makes the sentence true.

Example:

A sentence that has a variable in it, such as 10 + x = 15, is called an open sentence. To solve an open sentence, replace the variable with a number that makes the sentence true. The number that makes the number sentence true is called the solution. The solution of 10 + x = 15 is the number 5.

Example 2: Example 3 Example 3::

12 + = 55 17 = – 8 14 = – 9

Solution = 55 – 12 = 43 17 + 8 = 25 14 + 9 =

= 43 so = 25 . So = 23