In adding fractions, make sure that the denominators are same... If the denominators aren't same find the LCM- Least Common Multiple of the denominators or their LCD - Least Common Denominator..
For example 2/3 + 3/4 = N
The LCM= 3- 3, 6, 9 ,12 ,15
4- 4, 8, 12, 16, 20
/12= 12÷3=4 x 2 = 8/12
/12= 12÷4=3 x 3 =+ 9/12
17/12= 1 5/12
In doing lowest term of fraction, get their GCF - Greatest Common Multiple..
For example 4/8 GCF=4
4 ÷ 4 = 1
8 ÷ 4 = 2