Bonjour
a. 3/7 + 15/7 x 3/2
= (3 x 2) / (7 x 2) + 45/14
= 6/14 + 45/14
= 51/14
b. 9/5 x (1/4 - 5/12)
= 9/5 x [(1 x 3) / (4 x 3) - 5/12]
= 9/5 x (3/12 - 5/12)
= 9/5 x (- 2/12)
= - 18/60
= (6 x - 3) / (6 x 10)
= - 3/10
c. (3/8 + 7/5) : (9/4 - 5/3)
= [(3 x 5) / (8 x 5) + (7 x 8) / (5 x 8)] : [(9 x 3 ) / (4 x 3) - (5 x 4) / (3 x 4)]
= (15/40 + 56/40) : (27/12 - 20/12)
= 71/40 : 7/12
= 71/40 x 12/7
= 852/280
= (4 x 213) / (4 x 70)
= 213/70.
