To subtract mixed numbers with different denominators, follow these steps:
1. Rename the fractions using a common denominator.
2. Subtract whole numbers from whole numbers. You might need to regroup first.
3. Subtract fractions from fractions.
4. Simplify, if needed.
Let's try it with

First, rename the fractions using a common denominator. The least common denominator of these fractions is 20. Multiply to make equivalent fractions with 20 as the denominator.

Rewrite the problem and subtract the whole numbers.

Now, subtract the fractions. Subtract the numerators and keep the denominator the same.

This answer is already in its simplest form, so there is no need to simplify it.