Answer:
The cashier is wrong

Explanation:
Given



Solving (a): Is the Cashier's step correct?
The cashier is wrong at step 2 because instead of calculating the sales tax, the cashier add the sales tax percentage to the total cost.
Solving (b):
First, calculate the total cost by adding the cost of jeans and shirt respectively:


Next, multiply the sales tax percentage to the total cost to get the sales tax amount.


Add the sales tax to the total, this gives the total payable amount.


approximated