Bonsoir,
1. -8/9 + 20/9 = 12/9 = 4/3
2. 12/5 - 1/15 = 36/15 -1/15 = 35/15 = 7/3
3. -8/3 + -1/2 = -16/6 -3/6 = -19/6
4. 4/7 - 2 = 4/7 -14/7 = -10/7
5. 13/12 - 10/9 =117/108 - 120/108 = -3/108
6. -2/3 - -8/3 = -2/3+8/3 = 6/3 = 2
7. 13/12 - 5/6 + 1/3 = 13/12 -10/12 +4/12 = 7/12
8. -5/4 * 3/7 = -15/ 28
9. 5/-42 * -7/3 * -12/25 = - 420/ 3 150 =- 42/315 = 14/ 105
10. -14/27 * -9/7 = 126/ 189 = 42/63= 14/63
11. 12 * 5/36
12. 5/8 * 3/2 + 11/16