The formula for area of a square is length x width. The x represents the width and the 7x is just the width times 7. this means the length is 7 times the width, If the width is x, then the length is 7x
Pit this in your calculator exactly like this 4,000(1.05)^5 and you get the answer 5,105.12625. So round your answer to the nearest dollar, which is 5,105.