Let X = the price he paid for the car.
For the amount of profit, multiply the price he paid ( X) by the percent of profit, so you would have 0.18x.
Now you have X + 0.18x = $4575
Add X and 0.18x to get 1.18x
Now you have 1.18x = 4575
Solve for x by dividing both sides by 1.18:
x = 4575 / 1.18
x = 3877.118
Rounded to the nearest whole dollar = $3,877