Bonjour,
A=
12*35 *36 =15 120
21* 8*5 = 840
=> 15 120/840 = 1 512/84 = 504/28 = 252/14 = 126/7
B=
5/3 - 14/12
= 5/3 - 7/6
= 10/6 -7/6 = 3/6 = 1/3
C=
1/2+3/4 = 2/4+3/4 =5/4
7/4 - 1 =7/4 - 4/4 = 3/4
( 5/4) / (3/4)
= 5/4 * 4/3
= 20/12 = 10/6 = 5/3
D=
7/3 * 18/ 15 = 126/45 = 42/15 = 14/5
14/5 -5/6 = 84/30 - 25/30 = 59/30
(5/12) / ( 59/30)
= 5/12 * 30/59
= 150/708 = 75/ 354 = 25/118