Answer:
a) 
b) 
Step-by-step explanation:
From the question we are told that:
3 coin are tossed
Therefore
Sample space 
Generally the sets that correspond with the result of at most one tail is therefore given as follows

Therefore
The result is at most one tail when

Answer: PEMDAS
Step-by-step explanation: You wanna add 1 to both sides and get 3√x = 1. Then you wanna multiply 3 by 3√x which leaves you with x cause it canceled out. But remember to multiply 3 on both sides so x = 1 sq rt 3. Which is just 1.
x = 1
The relationship between variance and standard deviation is :
Standard deviation = sqrt (variance),
Variance = standard deviation^2.
hope this help