The table below shows the cost of sending packages of various weight from 1995 to 1999. What is the cost of mailing a 6-ounce package?

In order to determine whether two expressions are equivalent to one another, they are equated using an equals to sign (=) and then simplified. Upon simplification, the expressions should yield a logical and true statement. For example, a simplified expression may present
2 = 2
If such a case is present, then we know that the expressions are indeed equal. However, if the two sides are not equal, lets say
2 = 3
Then the expressions are not equal.

By verifying expressions, we are usually able to cross check our solutions to problems and also determine whether the answer(s) obtained makes sense.