Would someone please explain to me how to solve these? I'm completely lost and can't even figure out one of the problems on my homework. I would greatly appreciate step-by-step instructions that are as non-confusing as possible.

A=115+1/2(p+s) solve for s=?

P=2w+2l solve for w=?

Also, this word problem:

Set up an equation for the given application problem.

The perimeter of standard - size copier papper is 99 cm. The width is 6.3 cm less than the length. Find the length and the width.

If you would like to just do one that's fine, I'm just in desperate need of some instructions.