Решение:
- \( -9x + 7x - 5x + 2x = (-9 + 7 - 5 + 2)x = -5x \)
- \( 5a - 6a + 2a - 10a = (5 - 6 + 2 - 10)a = -9a \)
- \( 11p + 2p + 20p - 7p = (11 + 2 + 20 - 7)p = 26p \)
- \( -3.8k - k + 3.8k + k = (-3.8 - 1 + 3.8 + 1)k = 0k = 0 \)
- \( a + 6.2a - 6.5a - a = (1 + 6.2 - 6.5 - 1)a = -0.3a \)
Ответ: а) \( -5x \); б) \( -9a \); в) \( 26p \); г) \( 0 \); д) \( -0.3a \).