Answer:
a) 3.5
b) 3.33
c) 
Step-by-step explanation:
As given,
A fair die is rolled 10 times
a)
Expected value of Sum of the number in 10 rolls = 
                                                                                 = 3.5
∴ we get
Expected value of Sum of the number in 10 rolls = 3.5
b)
Ley Y : number of multiples of 3 
Y be Binomial 
Y - B(n = 10, p =  )
 )
Now,
Expected value = E(Y) = np = 10× = 3.33
  = 3.33
c)
Let m = total number of faces in a die 
⇒m = 6
As die is roll 10 times
⇒n = 10
Now,
Let Y = number of different faces appears
Now,
Expected value, E(Y) = m - m
                                   = 