return to main page

Question

how can i return my main page after calculate?
or how can i prevent disappear the form after Click the button. So if i use alert command, my form lost when i click button. Also if i use document.write command, i cant return my main page. help me

https://code.sololearn.com/W7qm1jo3mMAw/?ref=app

Answer 1

https://code.sololearn.com/WUKb2iueWQ0h/?ref=app

Answer 2

Like so?

https://code.sololearn.com/W2A2K3gz6klf/?ref=app

Answer 3

even this can work
https://code.sololearn.com/WvHr3WP8p1gw/?ref=app