9. How about going to the beach for a change?

→ Why don't we + V = How about + Ving: gợi ý, đề nghị làm việc gì đó

10. Their address is at 83 Son Tay Street

→ address (n): địa chỉ

→ at + tên đường

11. If we don't protect the environment, we will destroy ourselves.

→ ĐK loại 1: If + S (số ít) + V (s/es), S + will + V

→ Unless = If not

9. How about going to the beach for a change?

How about + Ving? đưa ra ý kiến, đề nghị 

10. Their address is at 83 Son Tay Street.

One's address + be + địa chỉ 

at + địa chỉ cụ thể 

11. If we don't protect the environment, we will destroy ourselves.

Unless: trừ khi = If .... not 

If 1 :If + S + V1/s/es, S + will/ can/shall .. + V1 

`color{orange}{~MiaMB~}`