There are two layers of upper and lower bookshelves, and one bookshelf has two upper and lower level

Bookshelves come in a variety of types and designs, and here are some common types of bookshelves:

Fixed bookshelves: Traditional fixed bookshelves, usually made of wood or metal, are fixed to a wall or floor. They can come in different constructions and sizes, such as single-tier shelves, multi-layer shelves, corner bookshelves, etc.

Hanging bookshelves: Hanging bookshelves are supported by brackets or hanging systems fixed to the wall. They are usually suspended in the air, saving floor space and can create a unique decorative effect.

Folding bookshelves: Folding bookshelves have the characteristics of foldable or coviable, which is convenient for storage and handling. When not in use, it can be folded up to take up less space.

Alcove bookshelves: Alcove bookshelves utilize wall space by building bookshelf space inside the walls. They often exist in a recessed form, adding a unique touch to the room.

Bookshelves on wheels: Bookshelves on wheels have bases with wheels or slides that make the entire bookshelf easy to move. This design facilitates the handling and rearrangement of books.

The above are just some of the common types of bookshelves, and in fact there are various creative and customized bookshelf designs that exist to suit different spaces and personal preferences. When choosing a bookshelf, you should take into account factors such as storage needs, space constraints, and décor style.

What's the problem, brother, arrange the size of An.

Supplement: There are 90 books on the upper floor.

120 copies of the ruler liquid.

A: There are a total of 120 books on the upper and lower levels. Baby.

Or supplemental conditions: 50 books on the lower level.

50x3 50 200 copies.

A: There are 200 books on the upper and lower floors.

To know how many books there are on the upper and lower floors, it is necessary to know how many books there are in total on the upper and lower floors.

Set: the original x book of the lower layer, the original book of the upper layer, according to the title Lu Liang Weimu:

But the slag can be carried: x=80, so the upper layer originally had 120 books, and the lower layer originally had 80 books.

You've even mentioned this question. 。x=80.120 on the upper floor and 80 on the lower floor

There are 12x books on the middle floor.

15x+12x+14x=410

x=10.

Upper layer 15x = 150 copies.

Middle layer 12x = 120 books.

The lower layer 14x=140 and the spring is absolutely resistant.

Setting: There were originally x books on the lower floor, and 3x books on the upper floor.

3x-40=2(x+40)

3x-40=2x+80

x=1203 120=360 (Ben).

360 Hot Days v Prosperity Together by Offering Groups.

It is best to solve it with equations.

Set the original x book of the upper layer, then, the original 3x book of the lower layer, Hu Sui according to the theme, get:

x+30=3x-210, pants take.

2x=30+210

x=120.

Then, the upper layer originally had 120 copies, and the lower layer had 120 copies (120 3 = 360 copies).

90x2=180 (book) means that the upper layer has 180 more books than the lower layer, and the upper layer is 4 times that of the lower layer. 4-1=3...The upper layer has three more copies than the lower one, and three copies are 180 copies.

180 3 = 60 (book) each copy has 60 books, the upper layer is 4 copies, the lower layer is 1 copy 60x4 = 240 (book) 60x1 = 60 (book) there are 240 copies in the upper layer, and 60 copies in the lower layer are expected to be adopted.

It turns out that the upper layer has more than 90 + 90 = 180 copies.

So the lower 180 (4-1) = 60 copies.

Upper 60 4 = 240 copies.