The task is to generate the correct answer for a given math problem.
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Question: Problem: the average weight of a , b and c is 60 kg . if the average weight of a and b be 70 kg and that of b and c be 50 kg , then the weight of b is :

Answer: 60 kg


Question: Problem: a gambler has won 40 % of his 40 poker games for the week so far . if , all of a sudden , his luck changes and he begins winning 70 % of the time , how many more games must he play to end up winning 60 % of all his games for the week ?

Answer: 80


Question: Problem: a number is increased by 20 % and then decreased by 20 % . find the net increase or decrease per cent .

Answer:
4