You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.
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Question: Question: A tank holds x gallons of a saltwater solution that is 20% salt by volume. One Fourth of the water is evaporated, leaving all of the salt. When 5 Gallons of water and 10 gallons of salt are added, the resulting mixture is 33 1/3 % salt by volume. What is the value of x?

 Option A: 37.5

 Option B: 75

 Option C: 100

 Option D: 150

 Option E: 175

Answer: Option B


Question: Question: How much time will it take for an amount of Rs. 900 to yield Rs. 81 as interest at 4.5% per annum of simple interest?

 Option A: 2 years

 Option B: 3 years

 Option C: 1 year

 Option D: 4 years

 Option E: 5 years

Answer: Option A


Question: Question: There are n cities. What is the number of airlines that connected 3 different cities (airline from city A to city B is different with airline from city B to city A)?

 Option A: n(n-1

 Option B: n(n+1

 Option C: n(n-1

 Option D: n(n+1

 Option E: n(n-2

Answer:
Option E