you can separate them so 6-4 and 1/2 - 1/7
6-4=2
1/2-1/7 you need to find a common denominator- 14
As you need to multiply 2 by 7 to get 14 you multiply the 1 by 7 to get 7/14. For the 1/7, you need to times the 7 by two to get 14 so you times the 1 by 2 to get 2/14.
So you get 7/14-2/14, because you have the same denominators you just subtract the top numbers and leave the bottom so you get 5/14. Add the 2 from earlier and your answer is 2 5/14