You want to buy a book priced R108, but you find you only have R79 in your purse. Think of ways in which you can find how much money you still need. You do not have pen and paper or a calculator with you, and you do not want to rely on the salesperson to work it out. There are various ways in which you can reason to find the answer. Describe two ways you would go about making the calculations to determine how much more you need to purchase the book.