8 x 108 = 864
4 x 102 = 408
if you subtract 864 and 408, then you get 456. so there is your answer!
All of the centra angles in a regular polygon must add up to 360 degrees. Also, because you're told that it is a regular polygon, the "regular" indicates that all of the central angles will be the same. Divide 360 degrees by 18 degrees to get the number of central angles, which is the same as the number of sides. 360/18 = 20. Therefore, the polygon has 20 sides. Hope that helps!
So u multiply R by both side to get 10+4=5r. next you would do is combine like terms to get 14=5r. next you would divde 5 by 14 to get 2.8. r=2.8
