Answer:
I think it is a) exponential
L# = 1 + 3S#
8S# - 2L# = 10
8S# - 2(1 + 3S#) = 10
8S# - 2 + 6S# = 10
14S# = 12
S# = 6/7
L# = 1 + 3(12/14)
L# = 25/7
Since the probability of the coin landing leads is 1/2, simply cube 1/2 to arrive at your answer: 1/8.
You cube 1/2 because you must land heads three times in a row and each flip is independent from other flips.
