Both of these words may sound the same, but they both have two very different meanings. The second word is wrong because the word fair means that someone or something is similar to being equal treated, sometimes in an agreement.
On the other hand, the word fare means actually deals with money, so that is a good sign. This word basically means the price or cost of a passenger's pay for public transport (such as taxis, buses, etc.). Therefore this answer fits the space in the question.
