Diện tích một viên gạch là

\(30\times30=900\left(cm\right)\)

Diện tích của căn phòng là:

\(900\times200=180000\left(cm^2\right)\)

Đổi:  \(180000cm^2=18m^2\)

1)Avoid (use) using the infinitive after the expression '' It's no use''.

2)I (not see) haven't seen her since we (leave) left school.

3)Last night we (watch) were watching television when the power (fail) failed

4)You can trust me. I remember (send) sending the documents right after you signed it.

5)Hurry up or you (be) will be late for school.

6)All the tickets (sell) were sold out yesterday.

7)I'm going to bed. I (work) have been working for hours and I'm tired.

8)He stopped (buy) to buy a newspaper on the way home.

9)If you (tell) had told me it was her birthday, I'd have brought a present.

10)You (always leave) are always leaving the lights on. It's a terrible waste of energy

1. We have been cooking for the party for four hours.

2. If he had been careful, he wouldn't have lost his money.

3. John Speke didn't succeed in finding the source of the River Nile.

4. We are going to have the car repaired next week.

5. Mary asked John if he had ever read Harry Porter.

1/since

2/since

3.since

4.for

5.for

ko chặn dc 

3² . (x + 4 ) - 5² = 5 . 2²

9  . ( x + 4 ) - 25 = 20

9 . ( x + 4 )        = 20 + 25

9 . ( x + 4 )        = 45

     ( x + 4 )       = 45 : 9

      x  + 4          = 5

      x                 = 5 - 4

      x                 = 1

3.(x-8) = 106-25

3.(x-8) = 81

x-8 = 81:3

x-8 = 27

x=35

a

20 x 190 x 50

= 20 x 50 x 190

= 1 000 x 190

= 190 000

b , 

769 x 85 – 769 x 75

= 769 x (85 – 75)

= 769 x 10

= 7690