А)1/2+2/3+3/4=6/12+8/12+9/12=23/12=1 11/12
б) 7/8+1/6-2/3=42/48+8/48-32/48=18/48=3/8
в)9/10-3/5+5/7=63/70-42/70+50/70=71/70=1 1/70
г)5/24-1/60-1/40= 25/120-2/120-3/120 = 20/120= 1/6
ж)(7/10+3/5) - (1/6+2/3) = (7/10+6/10) - (1/6+4/6) =
=13/10-5/10 = 39/30 - 25/30 = 14/30 = 7/15