A) 7/5+11/2+3/20-21/4=(4*7+10*11+1*3-5*21)/20=(28+110+3-105)/20=36/20=
Simplificam cu 4 si obtinem 9/5
B)21/4+31/5+3/20-3/10=(5*21+4*31+1*3-2*3)/20=(105+124+3-6)/20=226/20=113/10
Simplificam cu 2
D) 11/25-7/100+1/5-3/20=(4*11-1*7+20*1-3*5)/100=(44-7+20-15)/100=42/100=21/50
Simplificam cu 2
E)5/9+7/6+9/4+6/36=(4*5+6*7+9*9+1*6)/36=(20+42+81+6)/36=149/36
F) 7/150+11/50+1/300+23/100=(2*7+6*11+1*1+23*3)/300=(14+66+1+69)/300=150/300=1/2
Simplificam cu 150