"Is that ok with you?", "Is that ok for you?", "Are you ok with that?"....what's the difference?
If it mention to the meeting time, which one is correct or be used more common?

Question

Answer

Is “something” OK “with/by/for” you?
To me they are all OK. 
But technically I think when a person asks (Is “something” OK “with” you?), you're the only person whose opinion is asked. While in (Is “something” OK “by” you?), the opinion of someone else, rather than you, may be important as well.

Answer

"Is it okay with you" sounds more correct because since its a meeting the word 'it' refers to a specific thing at the present time, whereas "that" would implicate something which probably is outside the parameters of the meeting that is taking place right now.

Answer

I suggest the last sentence... In meetings, you don't often use "is that okay with you" or "is that okay for you"

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