Can anyone me understand this?
i need understanding part b..

The 20th expression would be 80. Counted on my fingers xD hit 80 when i did 20 fingers. which means that if you put 20 as n, it should come out to 80, but it comes out to 84 by the answer you chose, so I'm wondering if the answer you chose was right, or if it was A 

Your answer would be ahere is how: perimeter is how long all the sides are. in a rectangle, there are two sets of parallel sides. so, to find this, we would to the following.(15x2)+(4x2)30+838if you have questions ask! and mark me brainliest! i really wanna level up : 3