When adding fractions, you have to make sure the bottom numbers are the same. Otherwise, you can't add them.
So currently, the bottom number for the first fraction is 5. The bottom number for the second fraction is 2.
As you can see, 5 is not the same as 2, so we need to find one number to make sure the bottom number is the same for both the fractions.
You can multiply the the first fraction by 2, and the second fraction by 5 to give you two fractions that have the same denominator (bottom number.)
So, 3/5 multiplied by 2 is the same as multiplying 3 by 2, and 5 by 2. That gives you 6/10.
1/2 multiplied by 5 is 1 multiplied by 5, and 2 multiplied by 5, which is 5/10.
Now that you have your converted fractions, you can add them and forget about the bottom number, as it's the same. When adding fractions, if the bottom numbers are equal, you leave it as it is, so the 10 stays as 10:
6/10 + 5/10 = 11/10
Notice how I added 6 and 5 to give me 11, but I don't add 10 + 10, because I don't need to.
on the side of 20 feet you have 5 fence posts each in including one on each of the corners. On the 35 feet side you would have 8 including the corners, but since the corner posts are done its 6 on each 35 feet side. So you get 5+5+6+6=22
