a car salesperson sells 7 cars on a Monday, and 8 cars on a Tuesday. This was 25% of the sales in that week. How many cars did the salesperson sell that week
Let X be the total number of cars sold in the week.
Thus, (7 + 8) / X = 0.25
This simplifies to 15 / X = 0.25
Multiplying both sides of the equation by X gives 15 = 0.25X
Dividing both sides of the equation by 0.25 gives X = 15 / 0.25 = <<15/0.25=60>>60
Therefore, the salesperson sold 60 cars that week. Answer: \boxed{60}.