When are they equal? A sale at [50% off plus an additional 25%] and a sale of 60-80%?

Alright, let's say there are two separate sales...

- One is "50% off items, and additional 25% off" (NOT the same as 75% off - It's 50% off, then another 25% taken off afterwards)

- Another is "60-80% off items"

At what point are they equal? Like, what number between 60-80% is equal to the (50% off + 25% off)?

Thanks
Question answered - Thank you very much, jackdog, for the timely response. (First answer received)