Let Wendy = 2 units, Brother = 3 units (since Wendy is \(\frac{2}{3}\) as old as her brother).
• Age gap = 3 units − 2 units = 1 unit
• 1 unit → 6 years
• Wendy this year = 2 units = 2 × 6 = 12 years old
• Next year, Wendy = 12 + 1 = 13 years old
Final Answer: 13