Вычислите удобным способом 6 класс

2) -2 3/4 + (+6,8) + (-1,25) + (+3 1/5)

1. -2 3/4 + (+6,8) = - 2 3/4 + 6 8/10 = - 2 15/20 + 6 16/20 = 6 16/20 - 2 15/20 = 4 1/20

2. 4 1/20 + (- 1,25) = 4 1/20 - 1 25/100 = 4 1/20 - 1 1/4 = 4 1/20 - 1 5/20 = 81/20 - 25/20 = 56/20 = 2 16/20 = 2 4/5

3. 2 4/5 + 3 1/5 = 5 5/5 = 6

==========================================================

3) - 5 1/6 + (+ 7 1/9) + (-4 1/3) + (-7 1/9)

1. - 5 1/6 + (+ 7 1/9) = 7 1/9 - 5 1/6 = 7 2/18 - 5 3/18 = 6 20/18 - 5 3/18 = 1 17/18

2. 1 17/18 + (- 4 1/3) = 1 17/18 - 4 1/3 = 1 17/18 - 4 6/18 = 1 17/18 - 3 24/18 = - 2 7/18

3. - 2 7/18 + (- 7 1/9) =  - 2 7/18 + (- 7 2/18) = - 9 9/18 = -9 1/2