How to compute rate of return/ discount

Question

I paid $100 for a gift card and received $150 gift card in return from vendor. 1) what is my profit percentage/rate of return and 2) when i use my $150 gift card how do i compute the discount the restaurant is giving me. I believe I'm making 50% regardless of how much my bill is; my friend believes my "discount" is 33.3%.

Answer 1

Buying a $150 gift card for $100 gives you a profit percentage/rate of return of 50%.