bonsoir
M=-1/2+7/4x5/9=-1/2+35/36=(-1x18)/(2x18)+35/36=-18/36+35/36=17/36
N=-5/3x(-4/7-(-9)/28)=-5/3x(-4/7+9/28)=-5/3x((-4x4)/(7x4)+9/28))
=-5/3x(-16/28+9/28)=-5/3x-7/28=35/84=(7x5)/(7x12)=5/12
P=(2/7-3/14)x(-5/6-2/9)=((2x2)/(7x2)-3/14))x((-5x3)/(6x3)-(2x2)/(9x2))
=(4/14-3/14)x(-15/18-4/18)=1/14x-19/18=-19/252
