Lena uses 3/5 eggs. she uses 2/3 for waffles. what fraction of the total number eggs does lena use

You want to find the total amount so you have to add them together 2/3 + 3/5. They don't have the same denominators so you would have to find the GCF (greatest common factor). You multiply the top and the bottom by 5 on 2/3 and multiply by 3 on 3/5. So if you rewrite the equation it would be 9/15 + 10/15. Since the denominators are now the same, you just add the numerators. Leaving you with 19/15.