某商店买进一批蚊香,按希望获利40%定价,卖出90%后,再打7折将剩余蚊香卖完,实际获利比希望获利少了15%

设买进这批蚊香要x元.
(（1+40%)*90%+(1+40%)*10%*7/10)X=x+40%*(1-15)%x+300
(1.4*0.9+1.4*0.1*o.7)x =x+0.34x+300
1.358x =1.34x+300
l两边同减去1.34x得 0.018x =300
x =16666.67元