Respuesta :

Let, S = Shirt, J = Jeans

14a) 
This question asks for the discount to be added after everything else.
S= 12   J=19

3S + 2J -3 = Cost with discount applied to total
^ This expression adds to costs, then takes away the $3 discount as the end.

14b)
This questions says the discount is added on every shirt, we get a similar expression:
3(S-3) + 2(J-3) = Cost with discount applied on every shirt and jeans

14c)
The difference between a) and b) is that:
 > the discount in a) is applied on the total, meaning a lower discount
> the discount for b) is applied on each shirt and jeans, meaning a greater discount

14d)
If I were the shop owner I would be more specific of what the discount included, for example we don't know whether to discount each product (shirts and jeans) or only discount the total.