Svp aider moi j'y comprends rien merci bonne soiré

P = - 27/36 x 35/18 x - 24/ -21
P = -3/4 x 35/18 x - 8/ - 7
P = ( - 3 x 35 x - 8) / 4 x 18 x - 7)
P = 840/- 504 = - 5/3

U : 60/100 x 2/3 = 120/300 = 2/5

N = 9/5 : 18/25 
N = 9/5 x 25/18
N = 225/90 = 5/2