Math Help - assistance with calculation z-score

1. assistance with calculation z-score

Hello guys,
I have the answer here and need explanation on coming to terms with it. The question,

5000 apartments sold in a certain area and the mean price is $459,000 and the standard deviation is$76000. A particular apartment has a z-score of 3.78. What did it sell for? – The formula to calculate z-score is (x -mean) / standard deviation. The answer that I have from the text book is $459,000+3.78*76,000=$746,280… but why?