Why didn't JavaScript carry out the calculation?

Question

https://code.sololearn.com/Wv3iOiIn9sVk/?ref=app

Answer 1

You forgot to add the ids to the inputs

Note- the placeholder is not the id

https://code.sololearn.com/Wrems126gHL0/?ref=app

Answer 2

OK!

Answer 3

Thank you Brain & Bones and Pariket.