问两道数学题~谢谢大家

csd9235

20. A car traveled 462 miles per tankful of
gasoline on the highway and 336
miles per tankful of gasoline in the
city. If the car traveled 6 fewer miles
per gallon in the city than on the
highway, how many miles per gallon
did the car travel in the city?
(A) 14
(B) 16
(C) 21
(D) 22
(E) 27
这道选B，完全不懂说的什么
17. Kim bought a total of $2.65 worth of
postage stamps in four denominations.
If she bought an equal number of
5-cent and 25-cent stamps and twice
as many 10-cent stamps as 5-cent
stamps, what is the least number of
1-cent stamps she could have bought ?
(A) 5
(B) 10
(C) 15
(D) 20
(E) 25
这道选C，不懂