GIVEN: A 3-digit number X74 is subtracted from a 4-digit number 1543 to get a 3-digit number YY9. CALCULATION: We need to check with the different values of X and see which value gives a result in which 1st two numbers are same. Put X = 9: 1543 – 974 = 569 Put X = 8: 1543 – 874 = 669 Put X = 7: 1543 – 774 = 769 Put X = 6: 1543 – 674 = 869 Put X = 5: 1543 – 574 = 969 Further values need not to check as they will give a 4-digit number. So, here it is evident that X = 8 and Y = 6 Now, XXY + YYX = 886 + 668 = 1554