【Question 4】
The sum of the digits of a three-digit number is 18, the hundreds digit is 1 more than the tens digit, and the units digit is 2 more than the tens digit. This three-digit number is $\qquad$.
【Analysis and Solution】
Sum and difference problem.
Hundred's digit + Ten's digit + Unit's digit $=18$;
Hundred's digit - Ten's digit $=1$;
Unit's digit - Ten's digit $=2$;
Ten's digit $=(18-1-2) \div 3=5$;
Hundred's digit $=5+1=6$;
Unit's digit $=5+2=7$;
The three-digit number is 657.