Respuesta :

KeiraDawn
The answer is 20 because if you add all of the numbers up and divide by three you get 20

Use Cosine Rule

12^2 = 18^2 + 28^2 - 2*18*28* cos C

cos C = (12^2 - 18^2 - 28^2) / (-2*18*28)

= 0.95635

m < C = 17 degrees