Pouvez vous m’aider svp je comprend pas mon exercice de math Merci

Bonjour

L = - 7/5 : (2/9 - 7/18)

L = - 7/5 : [(2 x 2) / (9 x 2) - 7/18]

L = - 7/5 : (4/18 - 7/18)

L = - 7/5 : - 3/18

L = - 7/5 x - 18/3

L = 126/15

L = (3 x 42) / (3 x 5)

L = 42/5

M = (4/5 + - 3/2) : (- 9/4 - 1/6)

M = [(4 x 2) / (5 x 2) - (3 x 5) / (2 x 5)] : [(- 9 x 3) / (4 x 3) - (1 x 2) / (6 x 2)]

M = (8/10 - 15/10) : (- 27/12 - 2/12)

M = - 7/10 : - 29/12

M = - 7/10 x - 12/29

M = 84/290

M = (2 x 42) / (2 x 145)

M = 42/145.