Answer
See below.
Work Step by Step
a) The mean of $n$ numbers is the sum of the numbers divided by $n$.
Hence the mean: $\frac{ 36+26+24+90+74}{5}=50$
b) The deviation is the difference of the data item and the mean.
Hence here the deviations: $ 36-50=-14, 26-50=-24, 24-50=-26, 90-50=40,74-50=24$
c) The sums of the deviations: $-14-24-26+40+24=0$
