Question

when 15 is added to double of a number the number become 3 times the original. find the number 

Answer 1

let the number be x.
 given 2x+15 =3x
         3x - 2x = 15
               x = 15
 the number is 15.

Answer 2

let the original number be x

therefore , 15 + 2x = 3x

=> 2x - 3x = - 15

=> - x = -15

x = 15

ANS > the original number is 15