B....................................................
K=10
Here is the equation
180-115=65
(4K+5)+(6k+10)+65=180
3420°
explanation:
the equation of the sum of interior angles are (n-2)x180
polygon above has 21 sides so you sub n as 21 and plug the equation in the calculator
First you should combine n/6-5n/12
that goes to 2n/12-5n/12 which equals -3n/12
then you should cross multiply -3n/12 by 1/16
12(1)=-3n(16)
12=-48n then solve for n by dividing by -48
-12/48=n simplify -1/4=n or -.25=n
