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).
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Question: Four letters picked without replacement from rsisririrsshs. What is prob of sequence iirr?

Answer: 3/715


Question: What is prob of picking 1 f and 2 n when three letters picked without replacement from {d: 1, f: 1, a: 2, n: 13}?

Answer: 39/340


Question: Three letters picked without replacement from {o: 11, p: 5}. Give prob of picking 3 o.

Answer:
33/112