To subtract mixed numbers, you first need to convert them into an improper fraction.
To do this, multiply the whole number (the integer, or 3 in my example) by the denominator and add the numerator to get the improper fraction.
1.
->
(3 times 2 is 6 + 1 is 7)
2.
->
(3 times 6 is 18 + 3 is 21)
Find a common denominator and adjust the numerators accordingly.
The LCD of 2 and 6 is 6. Our second fraction already has 6 as its denominator so just change the first one. Multiply 2 by 3 because 2 x 3 is 6. Whatever you do to the denominator, you must do to the top so multiply the numerator by 3. 7 x 3 is 21, so our new fraction is
.
Subtract the two improper fractions, and always simplify the result if possible
= 0
Hope this helps! :)