bonsoir
tu mettras niveau collège et pas lycée STP
( 3 - 2/3 ) : 28/3
= ( 9/3 - 2 / 3) x 3 /28
= 7/3 x 3 /28
= 21 / 84 = 1/4
( 2/3 : 5/6 ) - 2 /5
= (2 /3 x 6/5 ) - 2 /5
= 12/15 - 2 /5
= 12/15 - 6 /15
= 6/15 = 2/5
( - 3/4 + 2/4 ) : ( 4/10 - 25/10 )
= - 1/ 4 : - 21 /10
= - 1/4 x - 10/21
= 10/84
= 5/42
