1-3/28?(thats a fraction of 1 whole and -3 28ths)?

I am doing some fraction home work and I did all the working out to a question, this is the answer 1-3/28 (1 whole and -3 28ths) My maths teacher said that this is another question and you have to change it into a fraction that isnt. Does anyone know how to do this? If so please explain as I have to show my workings and I dont have a clue.Please help!