Question

If one tosses a coin three times, write dow nthe possible observed number of heads and their probabilities

Answer 1

You need to find the probability of Heads, Heads, Heads in 3 tosses;

P(HHH)= (1/2)(1/2)(1/2) <-- each toss has 2 possibilities and heads is one 
P(HHH)=1/8

Therefore, the probability of flipping 3 heads on a fair coin is 1/8 

Hope I helped :)