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).

[EX Q]: Calculate prob of sequence kkhh when four letters picked without replacement from khhhhkhhkhhhkkhhhh.
[EX A]: 13/306

[EX Q]: Let y(a) = -a + 5. Let m be y(3). Solve f + 16 = -0*f - 4*c, -3*c - 12 = -m*f for f.
[EX A]: 0

[EX Q]: Evaluate 6/12*-21*(-6)/(-9).
[EX A]:
-7