Minimization of Logical Equations
I'm not going to tell you too much; you show too little of your own efforts. Just a few basic tips to get you started.

You'll have to start with the truth table. With 3 inputs you have only 8 combinations. Start without the borrow bit (the half of the table for which it's zero). Then subtracting shouldn't be too hard: what's the result if you subtract 0 from 1? Or 1 from 1? If you want to introduce the borrow bit it could be useful to do the subtraction of two decimal numbers, that should be familiar since elementary school. Observe how the result is different with or without borrow. Keep it simple: 25 - 13 is without borrow, 25-17 is with borrow. That should get you started.