Hey there!
1. 5(s-2) This is because s-2 is the length of each side, and there are 5 sides in a pentagon all of that length, so multiplying it by 5 like this shows its perimeter.
2. 5s-10 This can be found by distributing the first equation, multiplying both s and -2 by 5.
3. (s-2) + (s-2) + (s-2) + (s-2) + (s-2) Each grouping in the parenthesis represents each of the 5 sides, so adding them all together will get you the perimeter.
4. 5(s) + 5(-2) This one is most like the first one, except it's a little more spread out. Multiply the term s by the 5 sides in one grouping, and the integer -2 by 5 in the other.
Hope this helps!