Given a simple high-school level math question, you are required to solve it and provide the final answer. The final answer is always a single number. These questions can range from a variety of topics like simple arithmetic, solving equations, converting a quantity from one unit to another, finding remainders/GCD/LCM, finding probabilities etc. Each question has only one correct answer. This answer can be a positive or negative integer, a fraction or a decimal number. If the answer is a negative number use the hyphen (e.g. -42) symbol for the minus sign. For decimal numbers, do not add extra zeros after the decimal point. For fractional numbers, separate the numerator and denominator using a forward slash (e.g. 3/25).

[Q]: Four letters picked without replacement from bbbsbbbsbbkkkssbbb. What is prob of picking 2 s and 2 b?
[A]: 11/102


[Q]: Four letters picked without replacement from aaaafaffaaafaa. What is prob of sequence fafa?
[A]: 45/1001


[Q]: Four letters picked without replacement from {r: 19, t: 1}. What is prob of picking 3 r and 1 t?
[A]:
1/5


