Bonjour

A = (- 12/14 + 20/35) x 98/25

A = [(- 12 x 5) / (14 x 5) + (20 x 2) / (35 x 2)] x 98/25

A = (- 60/70 + 40/70) x 98/25

A = - 20/70 x 98/25

A = - 1960/1750

A = (70 x - 28) / (70 x 25)

A = - 28/25

B = 3/15 - 42/5 x (- 5/14 + 5/21)

B = 3/15 - 42/5 x [(- 5 x 3) / (14 x 3) + (5 x 2) / (21 x 2)]

B = 3/15 - 42/5 x (- 15/42 + 10/42)

B = 3/15 - 42/5 x - 5/42

B = 3/15 + 210/210

B = 3/15 + 1

B = (3 x 1) / (3 x 5) + (1 x 5) / (1 x 5)

B = 1/5 + 5/5

B = 6/5.