aide moi de maths stp? Merci d'avance

Bonsoir,

A = 21/4 - - 7/120 x - 48/49

A = 21/4 + 7/120 x - 48/49

A = 21/4 - 336/5880

A = 21/4 - (168 x 2) / (168 x 35)

A = 21/4 - 2/35

A = (21 x 35) / (4 x 35) - (2 x 4) / (35 x 4)

A = 735/140 - 8/140

A = 727/140

B = 3/4 x (- 3/5 + - 9/2)

B = 3/4 x (- 3/5 - 9/2)

B = 3/4 x [(- 3 x 2) / (5 x 2) - (9 x 5) / (2 x 5)]

B = 3/4 x (- 6/10 - 45/10)

B = 3/4 x - 51/10

B = - 153/40

C = - 2/3 + 3

        3/7 + 6

C = [- 2/3 + (3 x 3) / (1 x 3)] / [3/7 + (6 x 7) / (1 x 7)]

C = (- 2/3 + 9/3) / (3/7 + 42/7)

C = 7/3 : 45/7

C = 7/3 x 7/45

C = 49/135

Bonsoir,

A= 21/4 - ( - 7/ 120 ) x  ( - 48/ 49)

A=  21/4 - ( - 1/5 ) x ( - 2/ 7 )

A=  21/4  - (2/35)

A=  (21 x 35 - 2 x 4) / (4 x 35)

A= ( 735 - 8 ) /  140

A= 727 / 140

B=  3/4 (-3x2 - 9x 5 ) / ( 5 x 2 )

B=  3/4 ( -6 -45 ) / 10

B= 3/4 ( -51/ 10 )    

B= -153/40

C= [ (-2 +3x3)/ 3] / [ (3 + 6x7) 7 ]

C= (7/3) (7/45)

C= 49/135