In elementary school, you should write an answer at the beginning and the end.

Junior high school began to write the solution, don't write "the answer: ..." If it is a calculation problem or a proof problem, write it at the end, if it is an application problem.

High school is similar to junior high school, but you can simply draw conclusions about application questions, which is not as strict as writing and answering in junior high school.

I have always been like this. This problem has never been a problem, but it is the teacher who decides in the end, so you should listen to the teacher and it won't hurt you.