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]: Suppose 60*x + 70 = 65*x. Calculate the highest common factor of x and 21.
[EX A]: 7

[EX Q]: Two letters picked without replacement from xhtxihxghxhthxx. What is prob of sequence hi?
[EX A]: 1/42

[EX Q]: How many nanograms are there in 3/10 of a microgram?
[EX A]:
300