3/4+3/20

To add 2 fractions, you'll have to have the same
denominator.

The least common denominator is 20 =
4*5.

We'll multiply by 5 the 1st
fraction:

(3*5 + 3)/20

We'll
factorize by 3:

(3*5 + 3)/20 = 3(5 +
1)/20

We'll add what is inside
brackets:

3(5 + 1)/20 =
3*6/20

3(5 + 1)/20 = 18/20

3(5
+ 1)/20 = 2*9/2*10

3(5 + 1)/20 =
9/10

The result of adding the given fractions
is: 3/4+3/20 = 9/10.