when do I use ましょう vs ましょうか, they look almost the same

Question

textbook example: 手伝いましょうか。and then 一緒に食べましょう。in the very next page and I can't tell the actual difference in feeling

Accepted Answer

ましょう is a straightforward invitation/suggestion ("let's eat!"). ましょうか adds a question nuance, so it's more like "shall we?" or when offering to help someone, "shall I do it for you?" — 手伝いましょうか literally reads as "shall I help?", it's you offering, not you deciding for both of you

Answer

oh that's a great distinction, offering vs deciding together. thanks!