Average of 13 numbers = 68∴ Total of 13 numbers = 13 × 68 = 884Average 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