The question is 3 1/4 - 1 3/4. You can't subtract 1/4 from from 3/4 so you will have to borrow from 3. Once you have done that, your problem will look like this -
2 5/4 - 1 3/4. After you subtract you get - 1 2/4. Since we can simplify 2/4, the final answer will be 1 1/2. I hope this makes sense. Please ask me if you have questions or want me to go more in-depth with how I got the answer. Answer given by AMN1.