Question 200061
Adding and subtracting fractions are very simple, that is if yo know only one rule.
The rule is to have common denominators.

2/3+5/7
The common denominator for 3 and 7 will be 21. The easiest way is to just multiply them together. 
So you have 21, then you ask yourself. How many times did 3 go into 21. (7 times) So you multiply 2 by 7 as well. Same for the other side. How many times does, 7 go into 21. (3 times) So you  multiply 5 by 3.

Now you have.
14/21+15/21     Now you can add them as normal numbers. (Remember you don't add the denominators)

29/21
Reducing them are quite simple as well, all you do as subtract the top number from the bottom number.
1 and 8/21


3/4+7/12

Using the same steps you should start off with.
9/12+7/12
16/12
1 and 4/12 You can also simply simplify it to.....
1 and 1/3


4/9-1/8
32/72-9/72
21/72
7/24