TASK DEFINITION: Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.
PROBLEM: Problem: a solution of 70 litres contains oil and water in the ratio 9: x. if 6 litres of water is added to the solution, the ratio becomes 6: 4, find the value of x ?
Options: a. 6, b. 8.5, c. 9, d. 6.5, e. 5

SOLUTION: e

PROBLEM: Problem: a person crosses a 800 m long street in 5 minutes. what is his speed in km per hour ?
Options: a. 1.23, b. 2.86, c. 4.36, d. 9.25, e. 9.61

SOLUTION: e

PROBLEM: Problem: if 1 + 3 = 10; 3 + 5 = 52; 5 + 7 = 174 then 7 + 11 = ?
Options: a. 354, b. 225, c. 654, d. 741, e. 464

SOLUTION:
e