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).

Suppose 0 = 5*n - s - 13, 18 = -3*n + 6*n - 4*s. What is the lowest common multiple of 22 and 7 + (n - 3) - 0?
66

What is 81/4 of a kilometer in meters?
20250

Suppose -4*b + c = -b - 71, -b + 21 = -c. What is the tens digit of b?

2