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).

Example Input: Two letters picked without replacement from {n: 2, p: 1, s: 1, c: 2, d: 1, u: 1}. Give prob of sequence sc.
Example Output: 1/28

Example Input: Solve 96*r - 13 = 91*r + 2*u, 3*u - 12 = -3*r for r.
Example Output: 3

Example Input: Convert 39.13478 nanometers to kilometers.
Example Output:
0.00000000003913478