There are old man x and pear y. 3X+3=Y 4X-2=Y Solve equations, X=5, Y= 18, so there are five old men, 18 pears.

Binary linear equations refer to two linear equations with two unknowns. Each equation can be simplified as ax+by=c, which contains two unknowns (x and y), and the number of terms containing the unknowns is 1.

note:

1, the binary linear equation does not necessarily consist of two binary linear equations. More than one. It can also be composed of one or more binary linear equations.

2. Solving equation (department) application problems is an important aspect of combining mathematics with practice in middle school. The specific steps are as follows:

(1) Reading problem. Understand the meaning of the question. Find out what is a known quantity, what is an unknown quantity, and what is the equivalent relationship between the given and the involved problems.

(2) Dingyuan.

① Direct unknown

② Indirect unknowns (usually both). Generally speaking, the more unknowns, the easier it is to set up equations, but the more difficult it is to solve equations.

(3) The related quantity is expressed by an algebraic formula containing unknowns.

(4) Find out the equivalence relation (some given by the topic, some given by the equivalence relation involved in the problem) and list the equations. Usually, the number of unknowns is the same as the number of equations.

(5) Solve the equation and test it.

(6) answer. To sum up, the essence of solving application problems with equations (groups) is to first convert practical problems into mathematical problems (set elements and equations), and then solve practical problems caused by the solution of mathematical problems (list equations and write answers). In this process, the equation plays a connecting role. Therefore, the establishment of the equation is the key to solve the application problem.

3. Pay attention to the interaction between language and analytical formulas, such as "more", "less", "increase", "increase to (to)", "expand to (to)" and "expand". Another example is a three-digit number, where the hundred digits are A, the ten digits are B, the single digits are C, and the three digits are 650.

4. Pay attention to writing the equivalence relation from the language description: if X is greater than Y by 3, then X-Y = 3 or x = y+3 or X-3 = Y ... For another example, if the difference between X and Y is 3, then X-Y=3. 5. Pay attention to unit conversion such as "hours" and "minutes"; Consistency of s .v and t units, etc.