( 1- 1/ 13)x =(x-5-22)X3

x=39

Boys 39-5=34.

Class 39+34=73.

2. Analysis:

You can set the purchase price of the store as m, the selling price as n, and the profit = (selling price-buying price) ÷ buying price × 100%. According to the meaning of the question,

Find the equivalence relation, list the equations, use m to represent n, and then find the original profit.

Solution: you can set the purchase price of the store to be m and the selling price to be n, which is deduced from the meaning in the question.

(? ﹣? )÷? × 100%+ 10%=(? ﹣92%? )÷92%? × 100%,

Solution, n= 1. 15m,

So the original profit:

(? ﹣? )÷? × 100%=( 1. 15? ﹣? )÷? × 100%

= 15%

3. What is sold on the fourth day is what is left on the third day, so that 24 bags are 4/5 of what is left on the third day, so that 24/(4/5)=30 bags are left on the third day, and what is left on the third day is what is left on the second day, so that 30+24=54 bags are 3/4 of what is left on the second day, so that 54/(3/ 3) is left on the second day. So the 72+ 12=84 package is 2/3 of the first day, so the remaining 84/(2/3)= 126 package was sold on the first day, and the rest were all original, so126+12 =/kl.

The general formula is: (24/(1-1/5)+24)/(1-1/4)+12)/(1-65433.