Black pens = 70% of total.
Red + Blue = 100% − 70% = 30% of total.
Red = \( \frac{3}{10} \) of Blue, so Red : Blue = 3 : 10.

• Red = \( \frac{3}{13} \times 30\% = \frac{90}{13}\% \)
• Blue = \( \frac{10}{13} \times 30\% = \frac{300}{13}\% \)
• Black : Red : Blue = 70 : \( \frac{90}{13} \) : \( \frac{300}{13} \)
• Multiply all by 13: 910 : 90 : 300
• Simplify: divide by 10: 91 : 9 : 30

Final Answer: 91 : 9 : 30