Respuesta :

Answer:  3

Work Shown

x = some number

5x = five times that number

5x-6 = decrease by 6

5x-6 = 9

5x = 9+6

5x = 15

x = 15/5

x = 3

The mystery number is 3.

Check:

5*3 = 15

15-6 = 9

The answer is confirmed.