Bonjour
A) -3/5-8/14+6/12=
= -3/5 - (2 x 4)/(2 x 7) + (1 x 6)/(2 x 6)
= -3/5 - 4/7 + 1/2
= (-3 x 7 x 2)/(5 x 7 x 2) - (4 x 5 x 2)/(7 x 5 x 2) + (1 x 5 x 7)/(2 x 5 x 7)
= -42/70 - 40/70 + 35/70
= -82/70 + 35/70
= -47/40
B) 15/16-12/24+5/8=
= 15/16 - 12/(2 x 12) + 5/8
= 15/16 - 1/2 + (5 x 2)/(8 x 2)
= 15/16 - (1 x 8)/(2 x 8) + 10/16
= 15/16 - 8/16 + 10/16
= 25/16 - 8/16
= 17/16
C) 3/7-18/24+4/28=
= 3/7 - (3 x 6)/(4 x 6) + 4/(7 x 4)
= 3/7 - 3/4 + 1/7
= 4/7 - (3 x 7)/(4 x 7)
= (4 x 4)/(7 x 4) - 21/28
= 16/28 - 21/28
= -5/28
D) -15/35-4/6+5/7=
= -(3 x 5)/(7 x 5) - (2 x 2)/(2 x 3) + 5/7
= -3/7 - 2/3 + 5/7
= 2/7 - (2 x 7)/(3 x 7)
= (2 x 3)/(7 x 3) - 14/21
= 6/21 - 14/21
= -8/21
E) 1/5+3/2+5/4=
= (1 x 4)/(5 x 4) + (3 x 5 x 2)/(2 x 5 x 2) + (5 x 5)/(4 x 5)
= 4/20 + 30/20 + 25/20
= 59/20
