At first, Dave = 2u and Brother = 3u. After Dave gives $10, the new ratio is 1:2. Cross-multiply to find u.<br><br>[[model:questions/solutions/q4516.png]]<br><br>• After transfer: Dave = 2u − 10, Brother = 3u + 10<br>• Ratio (2u − 10) : (3u + 10) = 1 : 2<br>• Cross-multiply → 2(2u − 10) = 1(3u + 10)<br>• 4u − 20 = 3u + 10 → u = 30<br>• Dave at first → 2 × 30 = $60; Brother at first → 3 × 30 = $90<br><br>At the beginning, Dave had $60 and his brother had $90.<br>Check: 60 − 10 = 50, 90 + 10 = 100; ratio 50:100 = 1:2. ✓