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 #8# 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.
