3/4 * 5/7 = 15/28.
-8/11 * 5/3 = -40/33 = - 40/33 (mettre le - sur la même ligne que le trait de fraction).
-7/13 * -4/3 = 28/39.
-2/3 * 3 = -2/3 * 3/1 = -6/3 = -2/1 = -2.
-9/10 * 4/5 = -36/50 = -18/25 = -0,72.
-15/7 * -2/15 = 30/105 = 6/21 = 2/7.
-11/3 * 15/-36 * 24/-33 = -3960/3564 = 1980/1782 = 990/891 = 10/9.
-16/7 * 21/8 * 2/-15 = -672/-840 = 672/840 = 224/280 = 4/5 = 0,8.