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).

Two letters picked without replacement from dhxhhdhufehhfdexhe. What is prob of sequence xd?
1/51

What is prob of picking 3 o and 1 p when four letters picked without replacement from pooooopppppoo?
42/143

Suppose 2*p - 5 = 15. Suppose -2*d - 7 + 15 = 0. Calculate the smallest common multiple of d and p.

20