Ratio word problem

Hello, 

I am currently retaking my Maths GCSE atm via a distance learning course. The course lacks a lot of depth in the way they explain things, and doesn't show how they obtained the solutions, ie they are merely being stated outright. I am stuck on this ratio word problem, would you be willing to help?

Here's the question: 

The hotel bill for 4 people staying 7 days comes to £630. How much would 3 people who stayed 10 days have to pay?

I have developed several different answers but none of them are correct. Any help would be much appreciated.

Thanks for reading.:)

Student X

You can break things down by systematic reasoning. Some food for thought: 

If the hotel bill for 4 people staying 7 days comes to £630, then 4 people staying for 1 day would need pay £630/7 =£ 90 

In consideration of this,what happens if there is only a single person staying at the hotel for 1 day?  

Naturally he only pays his share which is equivalent to £ 90/4 =£ 22.5 

On the other hand, should this loner choose to stay at the hotel for a stretch of 10 days, the cost would come to £ 22.5*10 =£ 225 

I will leave you to figure out the rest, which shouldn't be all that difficult at this point.

Hope my explanation helps. Peace.

Best Regards,

Mr Koh