Adding fractions is done differently than the usual numbers. Normally, while adding or subtracting fractions you will find two types of problems:

Type 1: where the fractions being added have the same denominator eg.

Type 2: where the fractions being added have different denominators eg.

As you know, fractions represent parts of the whole. So, when these parts are from the whole broken into same number of parts it is easy to add them.
For Type 1 problems, we just need to add the top parts (numerator) of the fractions and leave the denominator as such. So, to solve the problem in the above example the solution will be:

For Type 2 problems where the denominator is different, we can not add these fractions by simply adding the numerators. In order to solve these problems first we will need to make into fractions with the same denominator. See how this is done in examples below.