The answer
15. She (travel) ....... has traveled ....... to six countries since she (start) ....... started .....the job.
->S + have/has + V3 +...... + since + S + V2
* I/ We/ You/ They/ Danh từ số nhiều + have
*He/ She/ It/ Danh từ số ít / Danh từ không đếm được + has
16. When in Japan, you should avoid (eat) ...........eating........... on the go.
-> Avoid + Noun/ Pronoun/ V-ing : Tránh khỏi điều gì
17. The Japansese tend (use) .... used .... their mobile phone discreetly when in public.
@vananh