1. Solve the equation according to its properties.

Properties of equation (1): When both sides of the equation add and subtract the same number at the same time, the equation still holds. This is the property of equation (1)

Properties of Equation (2): When both sides of the equation are multiplied or divided by the same number that is not 0, the equation still holds. This is the property of equation (2)

(1) Solve the equation according to its properties.

Example 1, solve the equation x+ 1.5 = 1 1 solution: x+1.5 =1-.

Summary: When the original left side of the equation is X plus a few, you can subtract a few from both sides of the equation at the same time when solving it, so that only X is left on the left side of the equation.

Example 2, solving the equation: x-2.8=7.2 solving x-2.8+2.8=7.2+2.8 x= 10.

Summary: When the original left side of the equation is X minus a few, you can add a few on both sides of the equation at the same time when solving it, so that only X is left on the left side of the equation.

(2) Solve the equation according to its properties.

Example 3, 2.5x=7.5

Solution: 2.5x÷2.5=7.5÷2.5 X=3.

Summary: the left side of the equation is multiplied by x, and the solution can be divided by several on both sides of the equation at the same time, leaving only the left side of the equation.

Example 4, x÷4= 13 solution: x÷4×4= 13×4 X=52.

Summary: When the left side of the equation is divided by X, it can be multiplied by several times on both sides of the equation at the same time, leaving only X on the left side of the equation.

2. Solve the equation according to the relationship between the numbers in addition, subtraction, multiplication and division.

① One Addendum = Sum-Another Addendum ② Minus = Minus+Difference ③ Minus = Minus-Difference ④ Multiplier = Product÷ Another Multiplier ⑤ Divider = Divider× Quotient ⑤ Divider = Divider ⑤ Quotient.

First, the solution of the addition and subtraction equation Example 5: X+4.2 = 8.9

Solution: x=8.9-4.2 X=4.7.

Summary: It turns out that X on the left side of the equation is an addend, and the solution can be based on one addend = and-another addend.

Example 6, x- 15= 12.5 solution; x= 12.5+ 15 X=27.5

Summary: It turns out that the x on the left side of the equation is the minuend, which can be solved according to the minuend = subtraction+difference. Example 7, 25.3-x= 13 solution: x=25.3- 13.

X= 12.3

Summary: In the equation, the original left x is a subtraction, and the solution can be based on subtraction = minuend-difference.

B, the solution method of multiplication and division equation

Example 8, 5x=25.5 solution: x=25.5÷5 X=5. 1.

Summary: It turns out that X on the left side of the equation is a multiplier, and the solution can be based on one multiplier = product ÷ another multiplier.

Example 9, x÷2.5= 13 solution: x= 13×2.5 X=32.5.

Summary: It turns out that X on the left side of the equation is dividend, which can be solved according to dividend = divisor × quotient. Example10,35 ÷ x = 7 Solution: x=35÷7 X=5.

Summary: The original left X in the equation is a divisor, which can be solved according to divisor = dividend.

Exercise questions:

solve an equation

X-7.7 = 2.85 X-3 = 68 X+ 10 = 25.5 X+ 13 = 45

x-0.6 = 8 x+8.6 = 9.4 52-x = 15 13÷x = 1.3

x+8.3 = 19.7 15x = 30 x+9 = 36 x-2 = 7

3x+= 12 18x = 36 12x = 27 5.37+x = 7.47

x÷3 = 5 30÷x = 7.5 1.8+x = 6 420-x = 170

3x = 18 x+9 = 40 6x = 36 1.5x = 3

54÷x = 8 40-x = 5 x÷5 = 2 1 5x = 3 1

x+2 = 80 x÷5 = 30 70÷x = 4 45.6-x = 1.6