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).

Four letters picked without replacement from {u: 9, s: 9}. Give prob of picking 3 s and 1 u.
21/85

Solve 0 = 3*f - 2*x - 11, 0 = 2*x - 7*x - 5 for f.
3

Convert 0.6599167 litres to millilitres.

659.9167