Explanation:
let the no be x and y
x+y=15
y=15-x.......eqn i)
x-y=3..........eqn ii)
putting value of y from eqn i ) to eqn ii)
x-y=3
x-(15-x)=3
x-15+x=3
2x-15=3
2x=18
x=9
no,putting value of x in eqn i)
y=15-x
y=15-9
y= 6
So,the value of x is 9 and y is 6