Can you tell me how long you have kept this book

Can you tell me how long you have kept this book

Could you tell me how long you will keep this book?
Keep is a continuous verb and borrow is a transient verb. Keep is used instead of borrow

English translation

They said: "They do not know where the book."
They said, "they don't know the book."

The number of boys in class 61 is 5 / 6 of the number of girls, which is equal to 3 / 4 of the number of students in class 62?

The number of boys in class 61 is 4 / 5 of the number of girls, which is equal to 3 / 4 of the number of students in class 62?
The number of boys in class 61 is
48 × 3 / 4 = 36 persons
So girls have
36 △ 5 / 4 = 45 people
Then there will be class 61
45 + 36 = 81

Calculating 72 times 85 + 27 times 85 + 85 with simple method

(72+27+1)*85

In the arithmetic sequence with 2n + 1 terms, if the sum of all odd terms is 165 and the sum of all even terms is 150, then n is equal to ()
A. 9B. 10C. 11D. 12

From the odd number term and S1 = (n + 1) (a1 + A2N + 1) 2 = (n + 1) × 2An + 12 = (n + 1) an + 1 = 165, ① even number term and S2 = n (A2 + A2N) 2 = n × 2An + 12 = Nan + 1 = 150, ② n + 1n = 165150, the solution is n = 10

There are 20 pieces of RMB 2 yuan, 5 yuan and 10 yuan, with a total of 122 yuan. There are as many pieces of RMB 2 yuan and 5 yuan. How many pieces of RMB 10 yuan
Urgent equations and processes

2 yuan and 5 yuan is x, 10 yuan is y
2X+5x+10Y=122 →7X+10Y=122
2X+Y=20 →Y=20-2X →7X+10（20-2X）=122→X=6 →Y=20-2*6=8

Fill in 6 / 7, 4 / 7, 2 / 7, (), 1 / 14, ()
The first one is 6 / 7, not 8 / 7

Divide the first number by 3 to get the third number, divide the third number by 4 to get the fifth number, divide the fifth number by 3 to get the seventh number, divide the seventh number by 4 to get the ninth number, and so on! Divide the second number by 3 to get 4 / 21, divide the fourth number by 4 to get 1 / 21. The answers are 4 / 21 and 1 / 21!

The sum of all numbers of a natural number n is denoted as s (n). If n + s (n) = 1993, the value of n is?

Because: n + s (n) = 1993, we can see that n is a four digit number, then the largest n is 9999, and the sum of the numbers is: 36. Therefore, it is not difficult to judge that the four digit number must be 19XX. At this time, 1 + 9 = 10. So let the four digit number be: 19ab + 10 + 10 + A + B = 19931900 + 10A + + 10 + B + A + B = 199311a + 2B = 83

Find the following indefinite integral ∫ (arctan e ^ x) / (e ^ x) DX

∫arctan (e^x)/(e^x) dx
=-∫(arctan (e^x) de^(-x)
=-arctan(e^x) / e^x + ∫ dx/(1+e^(2x) )
let
e^x= tany
e^x dx = (secy)^2 dy
∫ dx/(1+e^(2x) )
= ∫ [1/(secy)^2] .[(secy)^2/tany] dy
= ∫ (cosy/siny) dy
= ln|siny|+C'
= ln| e^x/√(1+e^2x) | + C'
∫(arctan e^x)/(e^x) dx
=- arctan(e^x) / e^x + ∫ dx/(1+e^(2x) )
=- arctan(e^x) / e^x + ln| e^x/√(1+e^2x) | + C

Find the rule to fill in the number 3:3:9:6:27:9: (): () find the number in ()?

81,12