Answer
See below.
Work Step by Step
The deviation is the difference of the data item and the mean.
a) Hence here the deviations: $29-49=-20, 38-49=-11, 48-49=-1, 49-49=0, 53-49=4, 77-49=28$
b) The sums of the deviations: $-20+(-11)+(-1)+0+4+28=0$
