bonsoir
3/4 + 5/8 = 6/8 + 5/8 = 11/ 8
24/35 * 21/90 = 504/3150 = 4/25
5/24 - 3/2 * 2/5 = 5/24 -6/10 = 25/120 - 72/120 = - 47/120
5 * 2/9 -7/2: 9/5 = 10/9 - 7/2 * 5/9 = 10/9 - 35/18 = 20/18 - 35/18 = - 15/18 = - 3/6
1 - ( 5 -14) / ( 15 - 7 ) = 1 - ( - 9/8) = 8/8 + 9/8 = 17/8