Answer:
a) P(three tails) = 
b) P(two tails followed by one head) = 
Step-by-step explanation:
coin is tossed three times so, outcome is
HHH, TTT, HTH, THH, HHT, THT, TTH, HTT.
Hence sample space will be
S = {HHH, TTT, HTH, THH, HHT, THT, TTH, HTT}
chance of getting three tails is '1' i.e. TTT
hence, 
 P(three tails) = 
two tails followed by one head is TTH
so, chance of getting that outcome is also '1'
 hence, 
 P(two tails followed by one head) = 