Follow these steps to know how to borrow whole numbers (minus):
1. add it, Instead of Minus
2. take your denominator and make it a whole.
eg. 1/4 make it 4/4
3.plus then minus
eg. 4/4 + 1/4 - 3/4
4. solve it like the one that i maed on top and then minus it and see what you get! (thats the answer)