1. I have cooked  since 3 years agos

⇒ The last time+S+QKĐ(khảng định)...+was+thời gian⇔S+HTHT(phu dinh)+since/for+...

2. how long have you bought that bag

⇒ When did+S+V?⇔ How long+have/has+S+$V_{II}$ 

    # đây nka. Cho ctlhn, 5 soa và tim nhé. Cảm ơn :3

                               ❤Chúc bn hok tốt❤

$\text{1. The last time I cooked was 3 years ago.}$

$\Rightarrow$ $\text{I haven't cooked for 3 years.}$

$\text{2. When did you bought that bag ?}$

$\Rightarrow$ $\text{When have you bought that bag ?}$

@vincent