The analysis process is as follows:

Plant a tree in each corner, ***4 trees, 3 trees on each side, *** 12 trees. Satisfy 3+2=5.

Formula: 4+3x4= 16, or 4x5-4= 16.

Multiplication:

(1) How much is it?

(2) How many times is a number;

③ Find the area and volume of the object;

(4) Find the fraction or percentage of a number.

Department:

(1) divide a number into several parts on average and find one of them;

(2) How many other numbers are there in a number;

(3) What fraction or percentage of a number is known to find this number;

(4) Find a number that is several times that of another number.