Use distribution to find the answer to this one.
5x * 6x² = 30x^3
5x * 3x = 15x²
5x * 7 = 35x
-1 * 6x² = -6x²
-1 * 3x = -3x
-1 * 7 = -7
30x^3 + 15x² + 35x - 6x² - 3x - 7 → simplify this using like terms (look at the exponent of x and if there even is one)
30x^3 stays becuase there is no other like terms
15x² - 6x² = 9x² becuase they are like terms
35x - 3x = 32x because they are like terms
-7 stays because ther is no other like terms
Put these together in the final answer: 30x^3 + 9x² + 32x - 7
Hope this helps!