1) 4 11/15+2 7/20= 2) 5 2/7-4 11/14=

1)
4 11/15 + 2 7/20 = (4 + 2) + (11/15 + 7/20) =
= 6 + (44/60 + 21/60) = 6 + 65/60 = 6 + 1 5/60 = 6 + 1 1/12 = 7 1/12,

2)
5 2/7 - 4 11/14 = (5 - 4) + (2/7 - 11/14) =
=  1 + (4/14 - 11/14) = 1 - 7/14 = 1 - 1/2 = 1/2