The sum of the two polynomials 6s^2t^2 + 2st^2 + 4s^2t + 3st^2 is
6s^2t^2 + 2st^2 + 4s^2t + 3st^2 = (6+4)s^2t^2 + (2+3)st^2 = 10s^2t^2 + 5st^2
The polynomials are being added term by term, and the coefficient of each term is being added.
The coefficient of s^2t^2 in the sum is 10, which is the sum of the coefficients of s^2t^2 in the original polynomials (6 and 4).
The coefficient of st^2 in the sum is 5, which is the sum of the coefficients of st^2 in the original polynomials (2 and 3).
So the sum of the polynomials is 10s^2t^2 + 5st^2, this is the final result.
It's important to note that the polynomials have to be in the same order of terms (same exponent) to obtain the correct result when adding them.