"Help do smth" vs "Help to do smth"

[Solver]

Dear teachers,

When I studied English at school I was taught to use "to" after the verb "help". At present, I come across a lot of phrases like "help do smth".
What is the correct form to use?

Thank you.

 

[5jj]

Both are acceptable nowadays.

 

[Solver]

5jj, thank you. Which variant is more preferable for formal style?