Bonjour

3/4-7/4  = - 4/4 = - 1

3/4-7/8 = (- 3 x 2) / (4 x 2) - 7/8 = - 6/8 - 7/8 = - 13/8

4/3-7/9 = (4 x 3) / (3 x 3) - 7/9 = 12/9 - 7/9 = 5/9

4/3-7/10 = (4 x 10) / (3 x 10) - (7 x 3) / (10 x 3) = 40/30 - 21/30 = 19/30

4/3-10/7 = (4 x 7) / (3 x 7) - (10x 3) / (7 x 3) = 28/21 - 30/21 = - 2/21

-4/3-10/11 = (- 4 x 11) / (3 x 11) - (10x 3) / (11 x 3) = - 44/33 - 30/33 = - 74/33.