Of the 720 students at a certain university, 25 percent are seniors. If x seniors were to graduate early and leave the university and no additional students entered or left the university, what value of x would reduce the number of seniors at the university to 20 percent?
Choose the most appropriate option.
A) 30  B) 36  C) 42  D) 45  E) 48

Rationale: sol : 180 - x = 20 % of ( 720 - x ) 4 x = 180 x = 45 answer : d
Answer: D