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).

Four letters picked without replacement from nknkknk. What is prob of picking 2 k and 2 n?
18/35

Suppose 0 = 4*t - 7*t + 1395. Let f be t/12 - (-1)/4. Suppose -4*c + 7 = -1, -n + 4*c = -f. Calculate the remainder when n is divided by 16.
15

Suppose -5*j + 318 + 17 = 0. Let p be j*3/(-6)*-2. Suppose -p = 2*c - 227. What is the highest common factor of 16 and c?

16