Question

(A) 13
(B) 15
(C) 17
(D) 18
(E) 19

Answer 1

se sao consecutivos entao y = x+1 e z = x+2 

x+/2 + x+1/5 + x+2/8 = 12
x = 14 
y=15
z=16     media 14+15+16 = 45   45/3 = 15 

Answer 2

x/2 + (x+1) /5 +(x+2) / 8= 12
 mmc:

  20x+8x+8+5x+10=480
         
         x= 14
         x + 1 = 15
         x+2 =16

  media : 15