In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: a certain car traveled twice as many miles from town a to town b as it did from town b to town c . from town a to town b , the car averaged 20 miles per gallon , and from town b to town c , the car averaged 25 miles per gallon . what is the average miles per gallon that the car achieved on its trip from town a through town b to town c ? 
Options: a ) 20 , b ) 18 , c ) 21.4 , d ) 16 , e ) 10
c

Problem: what is the average of first 21 multiples of 5 ? 
Options: a ) a ) 70 , b ) b ) 77 , c ) c ) 55 , d ) d ) 81 , e ) e ) 82
c

Problem: the number 523 fbc is divisible by 7 , 89 . then what is the value of f * b * c 
Options: a ) 504 , b ) 532 , c ) 210 , d ) 180 , e ) 280

d