(21/22-5/11)-(22/39-3/13)

1) 21/22 - 5/11 = 21/22 - 10/22 = 11/22 = 1/2 
2) 22/39 - 3/13 = 22/39 - 9/39 = 13/39 = 1/3 
3) 1/2 - 1/3 = 3/6 - 2/6 = 1/6
Ответ 1/6