The question does not specify whether it is EXACTLY 2 tails, or if more than 2 tails can be included as well (at least 2 tails).
There are only 88 possible combinations of heads and tails:
(Considering different orders)
3 " heads "color(white)(.................................)"HHH"
2 " heads "and 1 " tail "color(white)(...........) "HHT,HTH,THH"
1 " tail " and 2 " heads"color(white)(.............)color(blue)("TTH, THT, HTT")
3 " tails "color(white)(..................................)"TTT"
The probability has to be given as a fraction out of 8
There are 3 ways out of the 8 of getting exactly 2 tails
P(2 " tails") = color(blue)(3)/8
If there can be 2 or more tails:
3 " heads "color(white)(.................................)"HHH"
2 " heads "and 1 " tail "color(white)(...........) "HHT,HTH,THH"
1 " tail " and 2 " heads"color(white)(.............)color(blue)("TTH, THT, HTT")
3 " tails "color(white)(..................................)color(blue)("TTT")
P( "at least 2 tails") = color(blue)(4)/8 = 1/2" " in the simplest form.
The un-simplified denominator cannot be anything else but 8, because that is the total number of possibilities.
