-(-1/2)-49/50 -(+3/5)+(-9/10)=
=1/2-49/50-3/5-9/10=
=(1*25-49-3*10-9*5)/50=
=-99/50=-1,98
-19/24+7/8-41/72+5/6-1/3=
=(-19*3+7*9-41+5*12-1*24)/72=
=(-57+63-41+60-24)/72=1/72
11/18+5/9-1/2-13/15-47/90=
=(11*5+5*10-1*45-13*4-47)/90=
=(55+50-45-52-47)/90=-39/90=-13/30
-23/48+5/8-89/96-11/16+5/6=
=(-23*2+5*12-89-11*6+5*16)/96=
=(-46+60-89-66+80)/96=-61/96