请教数学题

rattledrum

a certain theater has 100 balcony seats. for every $2 increase in the price of a balcony seat above $10, 5 fewer seats will be sold. if all the balcony seats are sold when the price of each seat is $10, which of the following could be the price of a balcony seat if the revenue from the sale of balcony seats is $ 1,360?

A. $12

B. $14

C. $16

D. $17

E. $18

　　

解答是这样的：(10+2x)(100-5x)=1360

                        x1=3, x2=12

　　

题目说，if all the balcony seats are sold when the price of each seat is $10，不是说全部都卖10块钱？

rattledrum

我知道了