Adding fractions with unlike denominators ?

The fractions you start with have to be re-written with the same (common) denominator.

For example, if you were asked to add 3/5 and 6/7, you would:

1) Identify the Lowest Common Denominator (LCD):  Here it is 5*7 = 35.

2) Multiply both numerator and denom. of 3/5 by 7:  21/35

3) Mult. both num. and denom. of 6/7 by 5:  30/35

4) Combine these two equivalent fractions:   21/35 + 30/35 = 51/35 (answer)

 Try a few such problems yourself and write back if you need further help.