please help me with my pre algebra problem.... thinking of a number. see below

Question

Ryan is thinking of a number. If he multiplys this number by 6 and then subtracts 15 form the answer,
Ryan ends up with his original number.  What number is ryan thinking of?

 

use the steps of the 5 d process to answer this

 

describe/ draw

define/ do/ decide

and

declare?

Answer 1

????????????????????? "thanking" ????????????

6x-15=x

5x=15

x=3