instruction:
The task is to generate the correct answer for a given math problem.
question:
Problem: a diagonal of a polygon is an segment between two non - adjacent vertices of the polygon . how many diagonals does a regular 20 - sided polygon have ?
answer:
170', 'c ) 1425', 'd ) 2025', 'e ) 2500'

question:
Problem: a family pays $ 800 per year for an insurance plan that pays 70 percent of the first $ 1,000 in expenses and 100 percent of all medical expenses thereafter . in any given year , the total amount paid by the family will equal the amount paid by the plan when the family ' s medical expenses total how much ?
answer:
$ 1,400

question:
Problem: in a certain parking lot , 4 % of the cars are towed for parking illegally . however 80 % of the cars which are parked illegally are not towed . what percentage of cars in the parking lot are parked illegally ?
answer:
20 %