(30/x) - [30/(x+3)] = 1/2

chỉ em rõ cách giải được khum ạ

I. Choose the best answer A, B, C or D.

1. Unfortunately, my flight to Da Nang was ............... for one and a half hour.

A. delayed B. held up C. held on D. both A & B

2. Vietnam has a great number of tourist ...............; therefore, it is a good destination for many travellers worldwide.

A. attractive B. attractives C. attraction D. attractions

3. He had ............... two expeditions to Spain to study wild plants by the end of 2010.

A. taken B. made C. done D. gone

4. It can be quite busy here during  the tourist .

        A. Season B. phase C. period D. stage

5. Make  sure  you ahotel before you come to our island, especially in the summer.

    A. Book B. keep C. put D. buy

Giải thích giúp me luôn ạ thanks