1. (-3ab+6b-3c) + (7ab-6b+2c) = -3ab+6b-3c + 7ab-6b+2c = 4ab-c
(-3ab+6b-3c) - (7ab-6b+2c) = -3ab+6b-3c - 7ab+6b-2c = -10ab+12b-5c
2.(8x²+11x-1) + (3+5x-5x²) = 8x² +11x - 1 + 3 + 5x - 5x² = 3x²+16x+2
(8x²+11x-1) - (3+5x-5x²) = 8x²+11x - 1 - 3 - 5x + 5x² = 13x² + 6x - 4