A basic equality relation often used in solving practical problems is "two different formulas representing the same quantity"

A basic equality relation often used in solving practical problems is "two different formulas representing the same quantity"

This is the formula on the left side of the equation to be listed
For example, there are three fifths of boys in the class, six more than girls. How many students are there in the class?
If there are X students in the class, then there are 3x Boys / 5
”There are two ways to express "girl"
One is 2 / 5 of the class, that is, 2x / 5
The other is boys minus 6, that is 3x / 5-6
Both of them represent the number of girls, so they are equal. The equation is: 2x / 5 = 3x / 5-6

X-2 / 5 = 9,

2/（x-5)=9
9（x-5)=2
x=47/5

Check whether the number in brackets is the solution of the equation: 2x = 10-3x (x = 0x = 2x = 3)

I'll do it

Test whether the numbers listed in the following braces are the solutions of the corresponding equation: 3x-7 (x + 1) = 3-2 (x + 3) {3, - 2}

3x-7 (x + 1) = 3-2 (x + 3) = 3x-7x-7 = 3-2x-6
X = - 2, so the solution is - 2, 3 is not the solution, or can be substituted!