For aii) it should be $9 cheaper, not $36. You only subtracted the discounted price of 1 bag from shop Y instead of 2

b) should be asking what % discount to put if the discounted price for two bags is the same as shop X.


We know that the discounted price is $63 in shop X.


So if original price of two bags = $45 x 2 = $90,

Then the discount given has to be $90 - 63 = $27

27/90 x 100%
= 3/10 x 100%
= 3 x 10%
= 30%

The discount is 30%



Another way to do this :

First shop total discount = 10% of 1 bag + 50% of 1 bag with the same price
= 60% of 1 bag


But since we know in shop Y, both bags which have the same price ，must have the same discount,

This 60% must be divided equally among the two bags

60% ÷ 2 = 30%



You erased your working but I think it is correct actually