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]: Let g = 6 - 6. Let b = 3 + g. Suppose -w - b = -21. What is the tens digit of w?
[EX A]: 1

[EX Q]: Add together -0.1 and 637.
[EX A]: 636.9

[EX Q]: How many millilitres are there in twenty-one fifths of a litre?
[EX A]:
4200