You can use the midpoint formulae as I have in the picture below
Answer: CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
Step-by-step explanation: HOPE IT HELPS YOU
18 x 2 = 36
n = 12 x 2
n = 24
20/5+8^2*2-9
20/5+64*2-9
4+64*2-9
4+ 128-9
132-9
123
I hope this helped!
~cupcake