Question

3/8 - 1/7 =
9/12 - 2/5 =
15/18 - 2/9 =
12/13 - 1/2 =

Answer 1

I'll do the first for you, if you need, only then I'll continue.\[\Large {21 \over 56} - {8 \over 56} = {13 \over 56} \]

Answer 2

Ok, I will do the second one. Here it goes!

Answer 3

The answer is: 21/60

Answer 4

Here's the answers to the 3rd and 4th questions (what I've done is find a common denominator):

3. (11/18)

4. (11/26)