Answer:
1. (5x³+x²-3x-7)+(x²-6x+9) combine like terms
5x³+x²+x²-3x-6x-7+9
5x³+2x²-9x+2
2. (x²-8x+11)-(8x³+x²-5x-9)
-8x³+x²-x²-8x+5x+11+9
-8x³-3x+20
3. (3x³+7x²+6x)+(2x³+6x²+x)
3x³+2x³+7x²+6x²+6x+x
5x³+13x²+7x
4. (4x³+3x²+4)-(-7x³+11x²+12x)
7x³+4x³+3x²-11x²-12x+4
11x³-8x²-12x+4
5. (5x²-11x-3)+(2x²-11x+7)
5x²+2x²-11x-11x-3+7
7x²-22x+4
