1)а)3 3/4 +2 4/7= 15/4 + 18/7 = 105/28 + 72/28 = 177/28 = 6 9/28.б)2 4/9 - 1 5/6 = 22/9 - 11/6 = 44/18 - 33/18 = 11/18 2) 7 11/15 - (3 9/20 + 1 1/30) = 116/15 -( 207/60 + 62/60) = 116/15 - 269/60 = 464/60 - 269/60 = 195 / 60 = 13/4 3) 8 3/4 + (8 3/4 - 2 2/5) = 35/4 + ( 35/4 + 12/5 ) = 165/20 + ( 165/20 - 48/20) = 165/20 + 127/20 = 302/20 = 151/10 = 15.1 т