In a two-digit number, the digit at the units place is double the digit in the tens place. The number exceeds the sum of its digits by 18. Find the number.
Let ten's digit = x
Then units digit = 2x
and number = 10x + 2x = 12x
According to the condition,
12x = x + 2x + 18
12x - x - 2x = 18 ⇒ 9x = 18
x=189=2
∴ Number = 12x = 2 × 12 = 24