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 {i: 3, v: 2}. Give prob of sequence iv.
Example Output: 3/10

Example Input: What is prob of picking 1 u and 3 h when four letters picked without replacement from {r: 3, m: 4, h: 3, u: 1}?
Example Output: 1/330

Example Input: Solve -4*c = -2*r + 12, -r - 3*c - 10 = 9 for r.
Example Output:
-4