799$ is the 100% price of the camcorder & you want to find out how much would 7.5% of the total price is, then add it to the total price. More explanation on how to do it:
799$ --------> 100%
???? --------> 7.5%
Using cross Multiplication:
7.5 * 799 = 5992.5 / 100 = 59.925$
Now you know that the sales taxes = 59.925$
To find the total price of the camcorder (including the taxes), just add the sales taxes to the purchase price:
799$ + 59.925$ = 858.925$