I'm going to assume you just want answer three, sooooo
I'm in sixth grade and just finished this topic.
As you (probably) know, area is what is INSIDE the shape.
Perimeter is what the "border" is, so think of it as a border or an outline.
They already gave you the 2 1/2, so you can either do (options shown below) Also, since it is a square, you only add the four sides. (I guess that was pretty obvious)
2 1/2 + 2 1/2 + 2 1/2 + 2 1/2 (adding 2 1/2 four times)
OR
2 1/2 + 2 1/2 = 5 x 2 (adding 2 1/2 + 2 1/2, then multiplying by two.
OR
2 1/2 +2 1/2 = 5 + 5 (since you found out that 2 1/2 + 2 1/2 = 5, you can just add 5 + 5 since you would add the other two 2 1/2's anyway.)
Overall, the answer to number three is 10/Ten yards (don't forget the yards/ yds!)
Hope this helped. I have to finish my social studies homework now so I hope you do well!