First of all, make the numbers improper fraction so it is easier to work with. You now have 31/10 - 17/6. Then you need to find common denominators. To do this and find the Least common denominator, you will multiply the denominator 10 by the denominator of 6. You will multiply the numerator 31 by 6 as well and the numerator 17 by 10. You now have 186/60 - 170/60. When you subtract you get 16/10. Simplify. Your answer will now be 1 3/5.