Example 9

3

4

–

2

5

=

?

The fractions have unlike denominators. First, find the Least Common Denominator and rewrite the fractions with the common denominator.

LCD(3/4, 2/5) = 20

Multiply both the numerator and denominator of each fraction by the number that makes its denominator equal the LCD. This is basically multiplying each fraction by 1:

3

4

x

5

5

–

	2

	5

x

	4

	4

15

20

–

8

20

=

	7

	20