Let the numbers be of the form 100a+10b+c, where a, b, and c represent single digits. Then (100c+10b+a)-(100a+10b+c)=198 99c-99a=198 c-a = 2. Now, a can take the values 1-7. a cannot be zero as the initial number has 3 digits and cannot be 8 or 9 as then c would not be a single-digit number. Thus, there can be 7 cases. B can take the value of any digit from 0-9, as it does not affect the answer. Hence, the total cases will be 7×10=70