Bonjour
a. (3 - 2/3) : (4/3 x 7)
= [(3 x 3) / (1 x 3) - 2/3] : 28/3
= (9/3 - 2/3) x 3/28
= 7/3 x 3/28
= 21/84
= (21 x 1) / (21 x 4)
= 1/4
b. 2/3 : 5/6 - 2/5
= 2/3 x 6/5 - 2/5
= 12/15 - 2/5
= (3 x 4) / (3 x 5) - 2/5
= 4/5 - 2/5
= 2/5
c. (- 3/4 + 1/2) : (2/5 - 5/2)
= [- 3/4 + (1 x 2) / (2 x 2)] : [(2 x 2) / (5 x 2) - (5 x 5) / (2 x 5)]
= (- 3/4 + 2/4) : (4/10 - 25/10)
= - 1/4 : (- 21/10)
= - 1/4 x (- 10/21)
= 10/84
= (2 x 5) / (2 x 42)
= 5/42.
