The average of 12 numbers is 75. The average of the first 5 numbers is 68. The average of the next 5 numbers is 20% more than the average of the first 5 numbers. The 11th number is 12 more than the 12th number. What is the average of the 11th and 12th numbers?

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Accepted Answer

1. **Total sum:** $12	imes75=900$. 
2. **First 5:** $5	imes68=340$. Next 5 average = $68	imes1.2=81.6$, so next 5 sum = $5	imes81.6=408$. 
3. **Sum of first 10:** $340+408=748$. Last two sum = $900-748=152$. 
4. Let 12th be $x$. Then 11th = $x+12$. So $2x+12=152\Rightarrow x=70$, 11th = $82$. 
5. **Average of 11th and 12th:** $(82+70)/2=76$.

FINAL_ANSWER: b

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