You have 2/3 of a pan of brownies. You give away ¾ of what you have. What fraction of the whole pan have you given away?

Answer 1

multiply 2/3 by 3/4 = 6/12 = 1/2

multiply denominators to get 2x3=6, multiply denominators 3x4=12. 6/12 is one half of the whole pan.

But some of these questions have some ambiguity, such as what fraction of the "whole pan"

The whole pan or the original total amount was only 2/3. So maybe when you give away 3/4, that's all you've given away, just 3/4 of the original amount that you had. But if there was a whole full pan before you had only 2/3 of it, then the final amount you have is 1/2 of that whole full pan.