А)7 19/50 - 6,75 + 2,1 = 2,73
1)7 19/50 - 6,75 = 369/50 - 6,75 = 7,38 - 6,75 = 0,63
2)0,63 + 2,1 = 2,73
б)2 2/5 + 14 2/3 - 0,8 =16 4/15
1)2 2/5 + 14 2/3 = 12/5 + 44/3 =(12 × 3 + 44 × 5)/15 = 36/15 + 220/15 = 256/15 = 17 1/15
2)17 1/15 - 0,8 = 17 1/15 - 8/10 = 256/15 - 4/5 =(256 × 1 - 4 × 3)/15 = 256/15 - 12/15 = 244/15 = 16 4/15