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 ggrr when four letters picked without replacement from {r: 2, b: 6, t: 6, g: 4}.
[A]: 1/3060


[Q]: What is 0 + 5 - 15 - -5?
[A]: -5


[Q]: What is 21/4 of a microgram in nanograms?
[A]:
5250