ex 2
F = (3/5 + 5/6) : (11/6 - 2/5)
3/5 + 5/6 = 18/30 + 25/30 = 43/30
et
11/6 - 2/5 = 55/30 - 12/30 = 43/30
F = 43/30 : 43/30 = 1
ex 1
25/16 x (-12/15) = - (25 x 12) / 16 x 15 = - (5x5x4x3) / 4x4x5x3
= - 5/4
2/9 : (-5/3) = 2/9 x (-3/5) = - (2x3) / 9x5 = - (2x3) / 3x3x5 = -2/15
C = 1/4 - 3/5 = 5/20 - 12/20 = - 7/20
D = 8/3 - 2 = 8/3 - 6/3 = 2/3
E = -5/7 + 5/21 x 9/25
E = -5/7 + 5x9/21x25 = -5/7 + 9/105
E = -60/105 + 9/105 = -51/105 = -3x17/3x35 = -17/35
