(50-10) = (50-40) = 40 ÷10 = 4 (vehicle); 40x4-10 =160-10 =150 (person); A: A * * * has four cars; There are 150 students.

Profit and loss problem: it is not always possible to allocate several objects to a certain number of objects equally. If there are objects left, it is called surplus. If the object is not divided enough, it is called a loss. Any research on the application of profit and loss algorithm is called profit and loss problem.

Introduction to mathematics:

Mathematics [English: Mathematics, from ancient Greece μ? θξμα(máthēma)； Often abbreviated as math or maths], it is a discipline that studies concepts such as quantity, structure, change, space and information. Mathematics is a universal means for human beings to strictly describe and deduce the abstract structure and mode of things, and can be applied to any problem in the real world. All mathematical objects are artificially defined in essence.

In this sense, mathematics belongs to formal science, not natural science. Different mathematicians and philosophers have a series of views on the exact scope and definition of mathematics. Mathematics plays an irreplaceable role in the development of human history and social life, and it is also an indispensable basic tool for studying and studying modern science and technology.

Structure:

Many mathematical objects, such as numbers, functions, geometry, etc., reflect the internal structure of continuous operation or the relationships defined therein. Mathematics studies the properties of these structures, for example, number theory studies how integers are represented under arithmetic operations. In addition, similar things often happen in different structures, which is further abstract.

Then it is possible to describe the state of a class of structures with axioms. What needs to be studied is to find out the structures that satisfy these axioms among all structures. Therefore, we can learn abstract systems such as groups, rings and domains. These studies (structures defined by algebraic operations) can form the field of abstract algebra.

Because abstract algebra has great universality, it can often be applied to some seemingly unrelated problems. For example, some problems of drawing rulers and rulers in ancient times were finally solved by Galois theory, which involved the theory of presence and group theory. Another example of algebraic theory is linear algebra, which makes a general study of vector spaces with quantitative and directional elements.

These phenomena show that geometry and algebra, which were originally considered irrelevant, actually have a strong correlation. Combinatorial mathematics studies the method of enumerating several objects satisfying a given structure.