(x - 12) -15 = (20 - 7) - (18 + x)

x - 12 -15 = 20 - 7 - 18 - x

x - 27 = -5 - x

x - 27 + 5 + x = 0

2x - 22 = 0

2x = 0 + 22

2x = 22

x = 22 : 2 = 11

a) \(243^7\) và \(9^{10}.27^5\)

\(243^7=\left(3^5\right)^7=3^{35}\\ 9^{10}.27^5=\left(3^2\right)^{10}.\left(3^3\right)^5=3^{20}.3^{15}=3^{35}\)

Vì: \(3^{35}=3^{35}\) nên \(243^7=9^{10}.27^5\)

b) \(15^{15}\) và \(81^3.125^5\)

\(15^{15}=\left(3.5\right)^{15}=3^{15}.5^{15}\\ 81^3.125^5=\left(3^4\right)^3.\left(5^3\right)^5=3^{12}.5^{15}\)

Vì: \(3^{15}.5^{15}>3^{12}.5^{15}\) nên \(15^{15}>81^3.125^5\)

2. A

4. B

5. A

21. C

22. C

23. A

24. D

25. D

26. D

27. C

28. A

29. B

30. D

31. C

32. D

33. B

34. A

35. C

36. D

37. B

38. D

39. C

40. B

1. D

2. B

3. A

4. C

5. A

This house does is small but nice

---> This house is small but nice.

Last holiday I traveling to hanoi.

traveling ---> traveled

I like cook some food.

cook ---> cooking 

Xuan will visit her family tomorrow .

Câu này đúng nha!

At the moment, my sister reading books inthe room.

Thiếu: At the moment, my sister is reading books in the room.

I do not like eggs because it is not delicious.

it is ---> they are

I often do not go to school on sunday.

often do not ---> do not often

Why do not your mother travel on trip?

do not ---> doesn't