Algebric equations in worded text

I'm just having trouble trying to find the formulas, and I've left studying too late. There are a few, I won't post them all. Just wondering if there could be some hints on how to solve them, or how to find the formulas easier, when I find the formula I'm pretty much fine. I won't post them all, just a few, its a weekend and I know people won't want to help me too much :).

The sum of two natural numbers is 43. If the large number is three more than half the square of the smaller, find the numbers.

A rectangular room is to be tiled using 750 tiles. If the room requires 5 more rows of tiles along its length than it does along its width, find the nunmber of tiles along each side of the room.

A total of 2400 people are to be seated in a hall. The seats are arranged so that there are 50 more rows than there are seats across the hall. Find how many rows of seats are required.

A right-angled triangle is drawn so that the hypotenuse is 8cm longer than the shortest side. If the third side is 16cm, find the dimensions of the triangle.

If someone could work out the formulas, I'm basically fine, I just struggle finding them, thanks.