## Elementary Algebra

$800(19) + 800(2) + 800(4)(-1) =13,600$ In order to do this problem, we first multiply 800 by \$19 to find the price of the original set of shares. We then multiply 800 by two to account for the additional increase in price. Finally, we multiply 800 by 4 and -1 by 800 to account for the 1 dollar decrease in stock price, which occurred on four days.