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: the mean proportional between 4 and 16 is ?
Options: a. 12, b. 13, c. 14, d. 15, e. 16

SOLUTION: e

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: if ( a + b. = 12, ( b + c. = 9 and ( c + d. = 3, what is the value of ( a + d. ?
Options: a. 16., b. 8., c. 7., d. 6., e. - 2.

SOLUTION:
d