TASK DEFINITION: The task is to generate the correct answer for a given math problem.
PROBLEM: Problem: a merchant sells an item at a 20 % discount , but still makes a gross profit of 20 percent of the cost . what percent of the cost would the gross profit on the item have been if it had been sold without the discount ?

SOLUTION: 50 %

PROBLEM: Problem: if the average ( arithmetic mean ) of a and b is 45 and the average of b and c is 80 , what is the value of c − a ?

SOLUTION: 60

PROBLEM: Problem: a high school has 400 students 1 / 2 attend the airthmetic club , 5 / 8 attend the physics club and 3 / 4 attend the chemistry club . 3 / 8 attend all 3 clubs . if every student attends at least one club how many students attend exactly 2 clubs .

SOLUTION:
50