Your first question is strange. I suppose its not looking for a concrete answer. in the first case, just isolate s to one side.
Try this for the second one.
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.
Let x be length and y be width.
Perimeter = x+y+x+y = 2x+2y
Substituting, we get...
We know y is 6.3 less than this so,