The average of 13 numbers is 47. The average of the first 3 numbers is 39 and the next 7 numbers is 49. The 11th term is twice the 12th term, and the 12th term is 3 more than the 13th term. Find the 11th term.

Sum of all 13 numbers = 13 × 47 = 611. Sum of first 3 = 3 × 39 = 117. Sum of next 7 = 7 × 49 = 343. Sum of terms 11, 12, 13 = 611 - 117 - 343 = 151. Let x = 13th term. Then 12th term = x + 3, and 11th term = 2(x + 3) = 2x + 6. Sum: (2x + 6) + (x + 3) + x = 151. Solving: 4x + 9 = 151, so 4x = 142, and x = 35.5. Therefore 11th term = 2(35.5 + 3) = 45.5.