Question

123 is what percent of 321?

321/123=2.609756098 which rounds to 2.6%

2.6%= answer

Answer 1

wrong in so many ways.

First, 1.00 is 100%
.609 = 60.9%
so, 2.608 = 260.9%

But you read the question wrong. You know that 2 is 50% of 4, right?
So, you divide 2/4 = 0.5 = 50%

But you divided 321 by 123. Surely you could see that 2.6% is a totally unreasonable answer.

Actually, you should have divided 123/321 = 0.383 = 38.3%

Don't assume that just because you have arrived at an answer, it is correct. Take a step back and see whether it makes sense.