The ratio Boys : Girls = 5 : 12. Total children = 5 + 12 = 17 units.<br><br>
&bull; The total must be a multiple of 17<br>
&bull; Multiples of 17: 17, 34, 51, 68, 85, ...<br>
&bull; Between 60 and 70: only 68<br>
&bull; 17 units = 68 → 1 unit = 4<br>
&bull; Boys = 5 × 4 = 20<br>
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Final Answer: 20