Fiction = 8u = 1800. Non-fiction now = 1u = 225. Target is half of Fiction = 4u = 900, so we need 3u = 675 more non-fiction books.<br><br>[[model:questions/solutions/q4526.png]]<br><br>• Fiction = 8 units → 1800 books<br>• 1 unit → 1800 ÷ 8 = 225 books<br>• Non-fiction now = 1u → 225 books<br>• Target Non-fiction = half of Fiction → 1800 ÷ 2 = 900 books<br>• Additional needed → 900 − 225 = 675 books<br><br>675 more non-fiction books must be added.<br>Check: 225 + 675 = 900, and 900 is half of 1800. ✓