Adding fractions:
Lets say you have two fractions like 1/2 and 1/3. To add them, you have to make the denominator the same. So we find the least common multiple of 2 and 3, which is 6, so we multiple 1/2 by 3/3 so we have 3/6 without changing the value, and we multiple 1/3 by 2/2 to have 2/6. Then we add the numerators and have 5/6.
Subtraction fractions:
Same thing as adding, just subtracting instead.
Both need to make sure you have the same denominator.
Multiplying fractions:
This is the most simple. All you do is multiply the numerators and the denominators. So if you have 5/6 and 3/4, you multiply the numerators to have 15, the denominators to have 24, and so you have 15/24, simplified to 5/8.
Dividing fractions:
If you have 5/6 divided by 3/4, you flip the 3/4 to 4/3, and you multiply that with 5/6.