(2 5/7 + 9 2/3) : 4/7 = 21 2/3

1) 2 5/7 + 9 2/3 = 11 + (5/7 + 2/3) = 11 + (15/21 + 14/21) = 11 29/21 = 12 8/21

2) 12 8/21 : 4/7 = 260/21 : 4/7 = 260/21 * 7/4 = 65/3 = 21 2/3