31/6-11/2=
first change each mixed number to an equivalent improper fraction then find a common denominator and proceed as before leave your answer as an improper fraction be sure your answers are reduced to lowest terms

31/6 - 11/2 is the same as 31/6 - 33/6
31/6 - 33/6 = -2/6
-2/6 reduced is -1/3

(31/6) - (11/2) 

Note: In a fraction this is how it is set-up: 
numerator / denominator

The first common denominator you should always check is if the smaller denominator value can be multiplied by a number that would equal 6. 

In this case 2 can be multiplied by 3 to equal 6. 
So multiply both the top and bottom by 3. (The reason we multiply both the top and bottom by 3 and not just the bottom is because if we did that we would end up with something other than our original number. Seeing as in essence when you multiply by something over the same thing you are just multiplying by 1.)

(31/6) - (11/2) * (3/3) 
(31/6) - (33/6) 

Remember the smaller amount (31/6) is the positive number. Meaning our difference will be negative. 

(31/6) - (33/6) = (-2/6) 

We are not done! We need to simplify this fraction. Similar to how we multiplied by 1 we are going to "divide" the fraction by 1. 
This "division" is needed to put the fraction in the simplest form. (The simplest form being the form which can not be divided into a smaller fraction) 

So we need to find a number which is divisible by 2 and 6. It is 2 in this case. 

So divide each number in the fraction by 2. 

1/3 is our answer!

(Remember anything divided by itself (Like in the case of 2/2) is not 0, but instead it is 1!)