Average of 13 numbers = 68 ∴ Total of 13 numbers = 13 × 68 = 884 Average of last 7 numbers = 70 ∴ Total of last 7 numbers = 7 × 70 = 490 ∴ Average of first 6 numbers = 884 – 490 = 394 ∴Average of first 7 numbers = 63 ∴ Total of first 7 numbers = 63 × 7 = 441 ∴ 7th number = 441 – 394 = 47