Round each number to the nearest tenth, then subtract.<br><br>
&bull; 31.15: hundredths digit is 5, so round up → 31.2<br>
&bull; 7.56: hundredths digit is 6, so round up → 7.6<br>
&bull; 31.2 - 7.6 = 23.6<br><br>
Final Answer: 23.6