5/7- 1/2 (1/3 + 3/7)

Find the common denominator of the 7 and the 2 which is 14. 5/7 now becomes 10/14 and 1/2 now becomes 7/14. 10/14-7/14=3/14

Find common denominator for 3 and 7 which is 21. 1/3 now becomes 7/21 and 3/7 now becomes 9/21. 7/21+9/21=16/21

final problem is 3/14 X 16/21=48/294 which is reduced by dividing by 6= 8/49

answer is 8/49