on one's own

I solve the problem.

私は問題を解決します

I solve the problem on my own.

私は問題を自ら解決します

I solve the difficult problem on my own.

私は難しい問題を自ら解決します

I solve the difficult problem on my own without the teacher's help.

私は先生の助けなしに難しい問題を自ら解決します

I solve the difficult problem on my own without the teacher's help in the classroom.

私は教室で先生の助けなしに難しい問題を自ら解決します