Joe is 3 kg lighter than Chris, so Chris = Joe + 3. The total mass is both bars added.<br><br>[[model:questions/solutions/q2535.png]]<br><br>• Chris → 45 + 3 = 48 kg<br>• Total → 45 + 48 = 93 kg<br><br>The total mass of the two boys is 93 kg.<br>Check: 48 − 45 = 3 kg, and 45 + 48 = 93 kg. ✓