Question 797126
given that
    the sum of two numbers is 15 and difference of two numbers is 9

let X & Y be the two numbers

EQU:1  X+Y=15;
EQU:2  X-Y=9

ADD EQU:1 AND EQU:2

(X+Y)+(X-Y)=15+9
         2X=24
          X=24/2
          X=12

substitute X=12 in equ:1

        X+Y=15
       12+Y=15
          Y=15-12
          Y=3

therefore the required two numbers are 12 & 3

to check
12+3=15
12-3=9