Maths ( F.4)

P: orginal price
N: number of dozen can buy orginally for $900

PN= $900
so N=900/P
(P+150)(N-1)=900
(P+150)(900/P-1)=900
900-P+135000/P-150=900
-P+135000/P-150=0
P-135000/P+150=0
P2+150P-135000=0
P=300 or P= -450(rejected)
so the original price per dozen bottles of wine is $300

2007-02-06 20:54:50 補充：
the P2 in last 3 row mean P^2