Respuesta :

Answer: 15 hours (choice D)

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Work Shown:

(6 hours)/(8 trees) = (x hours)/(20 trees)

6/8 = x/20

6*20 = 8*x ... cross multiply

120 = 8x

8x = 120

x = 120/8

x = 15

It takes him 15 hours to plant 20 trees.