That's possible, but @SimonTsai 's sentence [supposed to] be able to solve the problem implies that more so than just should be able to...I think "should" means "you have obligation to know it."
还是要结合情景：我覺得"應該"可以解作類似should, 但在日常口語, 又不相同.
但中文既"應該", 語氣上, 會有不肯定的意思, 有點大致上會是.
" 这道题这么简单，你应该会做吧？ " 因為沒有了語氣, 但似乎是, "你無理由不會做吧???", 沒有一種強烈感, 而是有一種不質疑.
常說, 不要中文直譯英文, 要意譯..
我覺得, 英語比較少這種說法, 正常情況下, 不會語帶攻擊的, "串咀"說話... 沒有禮貌, 也太負面...
Yes, I do agree. That is why I used different colours for 'right' and 'are supposed to'. The first is to invite confirmation, rhetorically, and is thus more faithful to the Chinese original than the second, in my opinion.
You are right that it sounds peculiar with or without '吧'. To include '就', I may say, '既然老師教過，你就應該會做。'But using it in your original sentence: 这道题这么简单，你就该会做 (吧) ...