At first, Adults = 4u and Children = 5u. After 6 children alight and 6 adults board, the new ratio is 7:2. Cross-multiply to find u.<br><br>[[model:questions/solutions/q4514.png]]<br><br>• After change: Adults = 4u + 6, Children = 5u − 6<br>• Ratio (4u + 6) : (5u − 6) = 7 : 2<br>• Cross-multiply → 2(4u + 6) = 7(5u − 6)<br>• 8u + 12 = 35u − 42 → 27u = 54 → u = 2<br>• Passengers in the end → (4 × 2 + 6) + (5 × 2 − 6) = 14 + 4 = 18<br><br>There were 18 passengers on the bus in the end.<br>Check: Initial 8 adults + 10 children = 18; after: 14 adults + 4 children, ratio 14:4 = 7:2. ✓