bjr
a)
B/C = (2/3)/(1/5) = (2/3) x 5 = 10/3
A x (B/C) = (17/15) x (10/3) (on simplifie par 5)
= (17/3) x (2/3)
= 34/9
b)
A + B = (17/15) + 2/3) = (17/15 + 10/15) = 27/15 = 9/5
C + D = (1/5) + (7/4) = 4/20 + 35/20 = 39/20
(A + B)/(C + D) = (9/5) / (39 / 20) = (9/5) x (20/39)
= (9 x 20)/(5 x 39)
= (9 x 4)/39
= (3 x 4)/(3 x 13)
= 12/13
c)
17/15 + 7/4 + 1/5 -2/3 = 18/5 + 7/4 - 2/3 (dénominateur commun 60)
= (18 x 12)/60 + (7 x 15)/60) - (2 x 20)/60
= (216/60) + (105/60) - (40/60)
= (216 + 105 - 40)/60
= 281/60
