What to send?

I took the math, chemistry, and bio e subject test and got a 790, 760, and 800 on each respectively. Should I only send the math and bio e, or should I send all three?

It really does not matter. Send 2, send 3, it will not impact your application, IMO. Of course, if the college requires you to send all Subject Tests (although few do) or require 3 tests (even fewer) then you would need to send 3.

I can’t imagine a reason to not send a 760.

Is this a serious question?

Honestly, send them all if you can. They’re all fantastic scores.