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 picking 3 a and 1 o when four letters picked without replacement from {a: 1, t: 6, o: 2, m: 4, c: 3}.
[EX A]: 0

[EX Q]: Let z be ((-6)/4)/(3/(-6)). Let j(g) = -g**3 + 3*g**2 + g - 3. Let x be j(3). Let m be (-5 + x)*3/(-5). Solve 6*c - c = 5, -3*c + m = z*r for r.
[EX A]: 0

[EX Q]: In base 4, what is 21 + -30?
[EX A]:
-3