There were 48 students in a class, of which girls accounted for 3 / 8. Later, girls increased a number of people, and now girls account for 2 / 5 of the total number of students in the class

Female: 48 * 8 / 3 = 18 (48 + x) * 5 / 2 = 18 + X, that is, 6 = 3x, so x = 2
There are two more girls

There are 58 students in a class, of which 1429 are boys. Later, several girls are transferred. In this way, 815 are girls. How many are girls?

28 × 1429 △ 1-815-58, = 28 △ 715-58, = 60-58, = 2 (people). A: two girls are transferred

There are 45 students in class 2 of grade 6. The number of boys is two-thirds of that of girls. How many boys are there in class 2 of grade 6

What grade are you in? This problem can be solved by a system of equations. But I don't know if you have learned the system of equations
Setting: the number of male students is x, the number of female students is y
∴ x+y=45
x=2/3y
∴2/3y+y=45
y=27
∴x=45-27=18

1. There are 360 students in Grade 6, and the number of girls is 1 / 4 more than that of boys
2. To build a road, 1 / 20 of its total length was built on the first day, 0.5 km more on the second day than on the first day, and 4 km more on the second day. How many meters is the total length of the road?
Don't solve equations,

1. 360 ÷ (1 + 1 + 1 / 4) = 160 (male)
2. (4-0.5) / (1 / 20 + 1 / 20) = 35 km
I wish you progress in your study!
If you don't understand, please ask. If you understand, please adopt in time! (*^__ ^*)

There were 48 students in a class, of which girls accounted for 3 / 8. Later, girls increased a number of people, and now girls account for 2 / 5 of the total number of students in the class