Your answer is 35.75%.
Let’s pretend something at the store is $100. (It will save some math later)
100 - 35% leaves 65% (0.65 as a decimal)
100 x 0.65 = 65
That’s the price after the first discount. If we take 45% off of the sale price, we’ll be left with 55%, 0.55
65 x 0.55 = $35.75
Now normally you’d compare 35.75(sale price)/ 100(original price) to % off (x)/100, but doe this example, it’s unnecessary.
35.75/100 = x%/100