je ne n'arrive pas a resoudre ses calculs

6 -5/3-5/6 = 36/6 -10/6-5/6 = 36/6 -15/3 = 21/6 = 7/2

2+3/4+7/2 = 8/4+3/4+14/4 =25/4

7-9/5-13/25 =  175/25 -45/25 -13/25 = 175/25 -58/25 =117/25