Respuesta :

monniesop31mul

Answer:

13.5

Step-by-step explanation:

16x 9 = 144

x + (x+1) + (x+2)+ (x+3)+ (x+4)+ (x+5)+ (x+6)+ (x+7)+ (x+8) = 144

9x + 36 = 144

9x  =  108

x = 12

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(12 + 13 + 14 + 15)/4 = 13.5