Respuesta :

 let the numbers  x and y

sum of two numbers is x + y = 15     eq 1

given  {  one number is 3 less than so  :  y = x-3}


put in equation

x  + x -3  = 15

2x - 3 = 15

2x =  18

x = 9

y =  ( x-3 ) = ( 9 -3)  = 6

good job