7. Appling Gram-Schmidt method, it can decomposition vector = (3, −4) and = (4,3), α, β are real number. Please find the 2 × 2 matrix P, such that .

1. There was a class of 41 people divided into three groups A, B, and C, and the average score of subject natural’s test was 89.7 points; the average score of group A was 89.8 points; the average score of A, B combination was 88.5 points; the average score of A and C combination was 91 points, and how many people were in each of groups A, B and C?