Li Ming goes to the post office to buy greeting cards. Only when he got to the post office did he know that the price of greeting cards was reduced by 20%, so that he could buy eight more cards. How many greeting cards does Li Can Ming buy with his money now? Very easy to calculate:

Suppose Li Ming brings X yuan and the original price of the greeting card is Y yuan, then he can buy X/Y cards at the original price.

Now you can buy eight more cards when the price of greeting cards is reduced by 20%:

X / ( 1-20%) * Y = X/Y + 8

X/Y = 32。

You can buy it now: 32+8=40 yuan.