№368
а) ( 5/8 - 2/5 ) + 3/20 = (25/40 - 16/40) + 6/40 = 9/40 + 6/40 = 15/40 = 3/8
б) 1/8 + ( 5/9 - 1/4) = 1/8 + (20/36 - 9/36) = 1/8 + 11/36 = 9/72 + 22/72 = 31/72
в) 5/6 - ( 3/10 + 2/5) = 5/6 - (3/10+4/10) = 5/6 - 7/10 = 25/30 - 21/30 = 4/30 = 2/15
г) ( 3/4 + 1/8 ) - 5/8 = ( 6/8 + 1/8) - 5/8 = 7/8 - 5/8 = 1/4
№369
а) 3/25 + 0,34 - 4/25 = 3/25 + 34/100-4/25 = 12/100 + 34/100 - 16/100 = 30/100 = 3/10 = 0,3
б) 7/9 - 0,4 - 4/15 = 7/9 - 4/10 - 4/15 = 7/9 - 2/5 - 4/15 = 35/45 - 18/45 - 12/45 = 5/45 = 1/9