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: Calculate prob of sequence nesl when four letters picked without replacement from {a: 1, v: 2, e: 2, n: 1, l: 1, s: 1}.

A: 1/840
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Q: What is 15/4 of a millisecond in microseconds?

A: 3750
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Q: Solve 12 = -3*a + 9*a for a.

A:
2
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