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]: What is next in -63, -68, -75, -84, -95, -108?
[EX A]: -123

[EX Q]: Suppose 5 = -3*r - 4. Let b(f) = 3*f**2 + 2*f - 3. Let c be b(r). Calculate the highest common divisor of c and 6.
[EX A]: 6

[EX Q]: Three letters picked without replacement from hcafxfj. Give prob of picking 1 a and 2 f.
[EX A]:
1/35