Tyson saved 500 dollars for a week-long vacation. He did not keep close track of how much he spent the first three days. On the fourth day, he had 225 dollars. Write an equation to represent the amount he spent in the first three days.

A. 500 − x = 225

B. 500 + 225 = x

C. 225 − x = 500

D. 500x = 225

E. none of the above

Which one ??