Maintenance Requirement = 35% At what price level (P) would you get a margin call?

(10,000 P 50,000) / 10,000 P = .35 50,000 / 10,000 P = .65 P = 50,000 / 10,000 (.65) = 7.69

This was an example in a lecture slide we got I copy and pasted it, this is exactly how it was written in the slide. Can someone please explain this math? I'm am so lost with how these calculations were done.