a) (-1/9)+(+17/45)+(-11/6)+(+5/27)= -30/270+102/270-495/270+50/270
= -373/270
b)(-9/10)+(-7/12)+(+19/30)+(+1/5)= -54/60 - 42/60+ 38/60 +4/60= -54/60= -9/10
c) (-3/8)+(+1/16)+(-1/2)+(-3/4)= - 12/32 +2/32 -16/32 -24/32= -50/32= -25/16
d)(+5/4)+(-4/5)+(5/2)+(+7/10)= 25/20-16/20+50/20+14/20= 73/20