The barbs are 7 equal units. Three units are female, so the other 4 units are male = 12.<br><br>[[model:questions/solutions/q3410.png]]<br><br>• Male = 4 units → 12<br>• 1 unit → 12 ÷ 4 = 3<br>• Total = 7 units → 7 × 3 = 21<br><br>In total Max bought 21 tiger barbs.<br>Check: female = 3 × 3 = 9; 9 + 12 = 21. ✓