Final answer:
To find the sum of the given polynomials, combine like terms by adding the coefficients of the corresponding terms.
Step-by-step explanation:
To find the sum of the given polynomials (7x^3 - 3x^2 + 13), (12x^2 - 15x + 9), and (2x + 3), we simply combine like terms.
First, let's add the coefficients of the x^3 terms: 7x^3 + 0x^3 + 0x^3 = 7x^3.
Next, let's add the coefficients of the x^2 terms: 0x^2 - 3x^2 + 12x^2 = 9x^2.
Finally, let's add the coefficients of the x terms: 0x + 9x - 15x = -6x.
Combining the constant terms, we have 13 + 9 + 3 = 25.
Putting it all together, the sum of the polynomials is 7x^3 + 9x^2 - 6x + 25.