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

Q: Problem: if a speaks the truth 40 % of the times , b speaks the truth 80 % of the times . what is the probability that at least one will tell the truth

A: 0.12
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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: 
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Q: Problem: how many quarters are equal to 7 dollars ?

A:
28
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