The difference between a two-digit number and the number obtained by interchanging the two digits is 63. Which is the smaller of the two numbers? Choose the correct choice from the following answers:
A) 2
B) 3
C) 9
D) 7
E) 1
Explanation:   Let the ten's digit be x and units digit by y.   Then,   (10x + y) - (10y + x) = 63   9(x - y) = 63   x - y = 7   Thus, none of the numbers can be determined.   Answer: 7
<result>D</result>
The difference between a two-digit number and the number obtained by interchanging the two digits is 63. Which is the smaller of the two numbers?