Question 896413
let m = mean


m = 2.2 (given)




mean = Sum(value * probability)


m = 0*P(0) + 1*P(1) + 3*P(3) + x*P(x)


2.2 = 0*0.4 + 1*0.1 + 3*0.2 + x*0.3


2.2 = 0 + 0.1 + 0.6 + 0.3x


2.2 = 0.7 + 0.3x


2.2 - 0.7 = 0.3x


1.5 = 0.3x


0.3x = 1.5


x = 1.5/0.3


x = 5



So the missing value is 5.