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 prob of sequence dd when two letters picked without replacement from uddudd?
[EX A]: 2/5

[EX Q]: Calculate (-3)/6*10/15.
[EX A]: -1/3

[EX Q]: Let r be (0 + -1)*-1*1. Suppose 10 + 0 = 5*l. Suppose -4 = -l*u - 2. Calculate the greatest common divisor of u and r.
[EX A]:
1