In 20X8 there were only female clients, and there were 8,000 visits. The revenue was $200,000, so the price per visit was 200,000 / 8,000 = $25.
The question says that in 20X9, the price for female clients did not change. There were 6,800 visits and so the total revenue from them is 6,800 x $25 = $170,000.