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: $\frac{150+132+144+122 }{4}=137$
b) The deviation is the difference of the data item and the mean.
Hence here the deviations: $150-137=13,132-137=-5,144-137=7,122-137=-15$
c) The sums of the deviations: $13-5+7-15=0$
