Jane is making a suit which requires 2 5/8 yards for the jacket and 1 3/4 yards for the skirt. what’s the total amount of materials she needs

So when you have problems like this where there are two different fractions that dont directly go together, you find the common denominator or number on the bottom. So for these numbers it would be 16. 
You would multiply 8 by 2, and 4 by 4. Now that the denominators are the same, you would also multiply the numerator by the same amount as it's denominator. 
So now they would look like " 2 10/16 yards and 1 12/16. You now add these together to get:

4 6/16 yards. But you can't use this as an answer because it's not simplified, so you would try to get these fraction as low as possible, which in this case would look like 3/8

So the final answer would be 4 and 3/8 yards. I hope this helps :)