Given: The sum of the digits of a number is 18 less than the number Concept used: If the number is 'xy' It can also write 10x+y Where x is tenth place digit and y is unit place digit Calculations: Let the number be 'ab' So, Number =10a+b According to question a+b=10a+b–18 ⇒9a=18 ⇒a=2 ∴ The digit in the tens place of the number is 2