The task is to generate the correct answer for a given math problem.

[Q]: Problem: elvin ' s monthly telephone bill is the sum of the charge for the calls he made during the month and a fixed monthly charge for internet service . elvin ' s total telephone bill for january was $ 46 and elvin ' s total telephone bill for february was 76 $ . if elvin ' s charge for the calls he made in february was twice the charge for the calls he made in january , what is elvin ' s fixed monthly charge for internet service ?
[A]: $ 16


[Q]: 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 ?
[A]: 


[Q]: Problem: the simple form of the ratio 7 / 6 : 2 / 5 is ?
[A]:
35 : 1