Question 19What number should replace the question mark? Each row has five numbers around a central oval: 6, 8, [27], 7, 3; 9, 5, [21], 6, 4; 8, 7, [47], 9, 1; 6, 6, [20], 8, 2; 7, 9, [?], 5, 4. Answer with a natural number.