There are 180 books on the shelves in the library. If you take out 50 books from the lower shelf, there are as many books on the two floors. How many books are stored on the upper and lower floors respectively? Equation method:

Set upper x and lower180-x.

x= 180-x-50

The solution is x=65.

There are 65 upper-level books and 5 lower-level books11.

Formula method:

Upper layer =( 180-50)÷2=65 copies.

Lower layer =180-65 =115 copies.