The expression 12t^6-t^3+8t^6+4t^3-t^7-3t^3 has to be simplified.
12t^6 - t^3 + 8t^6 + 4t^3 - t^7 - 3t^3
=> 12t^6 + 8t^6 - t^3 - 3t^3 + 4t^3 - t^7
=> 20t^6 - t^7
The simplified expression is -t^7 + 20t^6
you take the like terms; 12t^6, 8t^6 and add the coefficients together creating 20t^6. Then add the other like terms -t^3, -3t^3, and 4t^3 and add them. These terms cancel out and the ^3 term becomes a zero. the last term -t^7 has no like terms so it stays the same. When you write the final answer, be sure that the terms go in order from largest power to smallest.