Analysis process:
Dong lent (Dong-18) yuan,
Lend Dongdong (money-108) yuan,
Encyclopedia price = English-Chinese dictionary price X 3,
D+(Dong-18)= encyclopedia price = D+Dong-18
Dong+(Ding Dingqian-108)= English-Chinese dictionary price = Dong+Ding Dingqian-108
Encyclopedia price-English-Chinese dictionary price = (D+D-18)- (D+D-108)
= 108- 18=90 yuan = English-Chinese dictionary price X 2, so English-Chinese dictionary price =45 yuan.
Encyclopedia price = English-Chinese dictionary price X 3=45 X 3= 135 yuan.
Finally, 108- 18=90 yuan, 90÷2=45 yuan, 45×3= 135 yuan.