The value of X = 1 , Y = 9 AND Z =8
Value of Z should be in place of zeroth. So X and Y should add upto 10. Combination of X= 1 and Y=9 gives 10.
Value of Z should be 1 less than Y so that when counting the 10th place, along with the carry gives Y as the result
1 1
9 9 +
8 8
1 9 8