Bonjour,
3/5 x 7/2 = 21/10
2/5 x - 5/7 = - 10/35 = (5 x - 2) / (5 x 7) = - 2/7
25/6 + 5/3 = 25/6 + (5 x 2) / (3 x 2) = 25/6 + 10/6 = 35/6
- 45/27 x 12/- 15 = 540/405 = (135 x 4) / (135 x 3) = 4/3
81/- 21 + 54/42 = (- 81 x 2) / (21 x 2) + 54/42 = - 162/42 + 54/42 = - 108/42 = (6 x - 18) / (6 x 7) = - 18/7.
