а) 1 9/10 + 3 1/10 = 4 10/10 = 5
б) 4 3/5 + 2 4/5 = 6 7/5 = 7 2/5
в) 6 - 3/5 = 5 5/5 - 3/5 = 5 2/5
г) 2 -1 4/9 = 1 9/9 - 1 4/9 = 5/9
д) 15 7/20 - 3 8/20 = 12 7/20 - 8/20 = 11 (20/20 +7/20) -8/20 =11 27/20 -8/20 = =11 19/20
е) 2 7/16 + 8/9 + 9/16 +1/9 = 2 + (63+128+81+16)/144 = 2+ 288/144 = 2+2 = 4