Classic Probability

Discrete Mathematics Level 2

A bag contains a number of coins, one of which is a two-headed coin and the rest are fair coins. A coin is selected at random and tossed. If the probability that the toss results in a head is $$\frac {7}{12}$$, then how many fair coins are in the bag ?

Details and Assumptions:
A two-headed coin is a coin which has head on both sides; a fair coin means it has tail on one side and head on the other.

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