1. I have seen her make a cake 
=>Cách 1 : She has been seen make a cake
Cách 2: A cake has been seen to her make
 2. She observes him do his homework
 =>He is observed do his homewwork
His homework is observed to him do
3. They are noticing them making fireworks 
=>They are noticed making fireworks
Fireworks are noticed to them make.
Chúc bạn học tốt. Cho mình xin câu trả lời hay nhất nhé