The task is to generate the correct answer for a given math problem.
--------
Question: Problem: if 5 a = 3125 , then the value of 5 ( a - 3 ) is :

Answer: 25

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: if jimmy drinks 8 ounces of water each time for 8 times a day . how much gallons of water he would have to prepare ahead to drink for 5 days ? ( 1 ounce = 0.0078125 gallon )

Answer:
2.5