1又1/4-0.78+2.75 =1 + 0.25 + 2.75 -0.78= 4 - 0.78= 3 .225又2/5+2又7/9-4.4= 5 + 0.4-4.4 + 2 + 7/9 = 3 又 九分之七4.8+3又5/6-1/6+5又1/5= 4.8 + 3+ (5/6 - 1/6) + 5+ 1/5= 4.8 + 0.2+ 8 + 2/3 = 13 又 三分之...