15 years ago, Lance was 1 unit and Father was 4 units. Now Lance is 2 units and Father is 5 units. The age gap of 3 units never changes, so 1 unit is the 15 years Lance aged.<br><br>[[model:questions/solutions/q4375.png]]<br><br>• 15 yr ago → Lance = 1u, Father = 4u, gap = 3u<br>• Now → Lance = 2u, Father = 5u, gap = 3u<br>• Gap unchanged → 3u = 3u, so the same unit size<br>• Lance grew → 2u − 1u = 1u = 15 years<br>• Lance now → 2u = 2 × 15 = 30 years old<br><br>Lance is 30 years old now.<br>Check: Father now = 5 × 15 = 75. 2/5 × 75 = 30. ✓ 15 yr ago: Lance 15, Father 60. 15 = 1/4 × 60. ✓