1. Formulated sub-algorithm: if you buy 3 kilograms of apples, you will get more money from 4 yuan, and if you buy 6 kilograms of apples, you will get less money from 8 yuan. The total price is equal to the unit price times the quantity. So the unit price is equal to the total price divided by the quantity. It costs more 12 yuan to buy three kilograms of apples, so the formula is: (8+4)÷(6-3) = 12÷3 =4 yuan.

2. Equation solving algorithm: let each kilogram of apples be X yuan. The money in the small red belt in the topic is certain, and an equation about unknown X can be listed. Buy 3 kilograms more apple 4 yuan, that is, the money for the small red ribbon is 3x+4, and buy 6 kilograms less apple 8 yuan, that is, the money for the small red ribbon is 6x-8, and the two formulas are equal. 3x+4=6x-8 gives x=4 yuan.

1. Mathematical formulas refer to formulas listed in numerical or algebraic calculations. In the primary school stage, the horizontal formula of the four operations is listed as vertical calculation, which means that a vertical formula is listed in the calculation process, which makes the calculation more convenient. And the sum of numbers is needed. Below the horizontal line, the sum should also be added horizontally. Four operations refer to the calculation rules of addition, subtraction, multiplication and division. The advantage of column verticality is that it can be calculated clearly. Matters needing attention in the mathematical formula are as follows: 1. Write the first addend on the top line first. If the two addends are different, write the number with more digits first. 2. Write the second addend on the next line. If the two addends are different, write the number with fewer digits. Write "+"before the second number. 4. The sign "=" in the formula is indicated by a horizontal line and written below the second number. 5. Write the calculation results of two numbers below the horizontal line and align them with the numbers above.

2. 1. An equation with an unknown number is called an equation, or an equation with an unknown number is an equation.

2. Holding the value of the unknown quantity of the equation is called the solution of the equation, or the root of the equation.

3. Solving the equation is the process of finding the values of all the unknowns in the equation.

4. The equation must be an equation, and the equation is not necessarily an equation. An equation without unknowns is not an equation.

5. Verification: After solving the equation, verification is needed. Verification is to substitute the unknown value into the original equation to see if both sides of the equation are equal. If they are equal, then the value obtained is the solution of the equation.

6. Note: Write the word "Xie", align the equal sign and check.

7. The equation depends on the relationship between the parts of the equation, and the relationship between addition, subtraction, multiplication and division (addend+addend = sum, and-where one addend = another addend, difference+subtraction = minuend, minuend-difference = subtraction, factor × factor = product, product/factor = another.