How do you subtract fractions with non common denominaters

To solve fractions with non common denominators you have to find the common one that they share. (Ex. If you have 4/5 - 7/10, you know that they can both have a common denominator of 10. To get the 5 in 4/5 to ten, multiply it by 2. Whatever you do to the top must happen to the bottom. So 4/5 = 8/10. Now you have 8/10-7/10 and you can do simple subtraction. 8-7=1. So your answer is 1/10.)