The shop declare a discount of 20% and later a discount of 15% after
first discount. total discount was?

Let, the original amount = x
First discount = x * 0.20 = 0.20x

Amount after first discount = x - 0.20x = 0.80x
Second discount = 0.80x * 0.15 = 0.12x

Amount after second discount = 0.80x - 0.12x = 0.68x
Difference would be: x-0.68x = 0.32x

So, Your Answer would be 32%

Hope this helps!