3/8+1/4=3/8+2*1/8=5/8
5/6+3/8+1/12=5*4/24+3*3/24+2*1/24=(20+9+2)/24=31/24=1целая 7/24
1/2+1/5+1/10=1*5/10+2*5/10+1/10=(5+10+1)/10=16/10=1целая 2/5
2/21+1/7+3/14+1/14=2*2/42+6*1/42+3*3/42+3*1/42=(4+6+9+3)/42=22/42=1/21
1/6+1/45+11/30+1/45+7/30=15*1/90+2*1/90+3*11/90+2*1/90+3*7/90= (15+2+33+2+21)/90=73/90