Michael owns 300 shares of a certain stock. Suppose the price of the stock drops by $4 per share. Write a multiplication equation to find the change in Michael's investment.

I put 300x(300x[-4]) is that right?

original value: 300x

new value: 300(x-4)

change = new-old = 300(x-4) - 300x = -1200

Makes sense, since each of 300 shares dropped in value by $4.

When you got your answer, did you think about how to check it?