Répondre :
1) 1/2 +14/15 : 2/3
= 15/30 + 28/30 : 2/3
= 43/30 : 2/3
= 43/30 x 3/2 = 129/60 = 43/20
2) (1/4+2/3 x 9/10) : 3/10
= (1/4 + 18/30) : 3/10
= 15/60 + 36/60 : 3/10
= 51/60 x 10/3
= 510/180
= 51/18
3) [(-2+1) x (-5)+4] - (-3)
= 5+4+3 = 12