最好是方程的
Last summer Sam worked for a cycle dealer.The dealer agreed to pay him $210 and a new bike
for seven weeks of work.But Sam didn't enjoy the job and quit after four weeks.The dealer
gave him $21 and the bike.How much was the bike worth?
(A) $216 (B) $225 (C) $231 (D) $253 (E) None of these