analyse

The length is expressed in letters: a.

The width is expressed in letters: b.

The base is represented by letters: H.

The height is expressed in letters: l.

Then length x width+bottom x height =ab+hl.

When letters are used to represent numbers, numbers are multiplied by letters, letters are multiplied by letters, and the middle multiplication sign can be omitted or indicated by "."; When multiplying letters and numbers, omit the multiplication sign and put the numbers in front of the letters; When "1" is multiplied by any letter, "1" is omitted.

Understanding of the formula:

1, a general format, is expressed by mathematical symbols. The formula of a certain relationship (such as law or theorem) between various quantities can generally be applied to the ways and means of similar things.

2, formula, in mathematics, physics, chemistry, biology and other natural sciences, using mathematical symbols to express the relationship between several quantities. It is universal and applicable to all similar problems. In mathematical logic, a formula is a formal grammatical object to express a proposition, but the proposition may depend on the free variable value of the formula.