Question

Don’t know how to do this

Answer 1

Okay, if the pizza costed you $5.68 plus 9% tax, the final price is written as $5.68 + (0.09 * $5.68) or 1.09 * $5.68 which would give you $6.912 which you would you have to approximate to $6.92. His error must have been some type of multiplaction error.

Answer 2

To figure out the cost including tax simply take the initial cost $5.68 and multiply it by .09 (which is 9%) to get

.5112.

Add this number on top of the cost of the pizza

5.68 + .5112 = $6.19 (rounded).

I do not know how Joseph got $17.16.