(7 - 4 5/13) - (4 - 2 1/13) = (91/13 - 57/13) - (52/13 - 27/13) = 34/13 - 25/13 =9/13
(8 - 4 13/20) - (6 - 5 3/20) = (160/20- 93/20) - (120/20 - 105/20)=67/20-15/20=52/20=
= 2 3/5
(5 - 2 7/19) - (4 - 3 2/19) = (95/19 - 45/19) - (76/19 - 59/19) = 50/19 - 17/19 = 33/19 =
= 1 14/19
(7 - 3 7/11) - (4 - 2 3/11) = (77/11 - 40/11) - (44/11 - 25/11) = 37/11 - 19/11= 18/11 =
= 1 7/11