a) =(14/90 : 14/9 + 2/15) x 30/21 = (1/10 + 2/15) x 30/21 = 3/21 + 4/21 = 7/21 = 1/3 = 0,(3).
b) = (4/10 - 16/10) x 10/3 + 3 = -12/10 x 10/3 +3 = -4 + 3 = -1.
c) = (112/90 x 15/7 - 36/10) x (-5/7)=(16/6-18/5) x (-5/7)= (-68/6) x (-1/7)=68/42=34/21.
d) = (2+1/18 - 11/24) x 9/73 +3/8 = 18/73 + 1/(73 x 2) - 33/(8 x 73) +3/8 = (144 +4-33+219)/(8x73)=334/584=167/292.
e) = (3/5 + 1/4 x 4/5) x (-15/4)= 4/5 x (-15\4) = - 3.