We have no way to calculate the probability of the coin being flipped three times. It really depends on who, where, when, and why.
But if it IS flipped 3 times, and it's an honest coin, then . . .
-- the probability of heads on the first flip is 0.5
-- the probability of heads on the second flip is 0.5
-- the probabilty of heads on the third flip is 0.5
-- the probability of all three results is
(0.5) x (0.5) x (0.5) = 0.125
That's 12.5% .
(or one eighth)