What is 300,000,000 is standard form

What could explain what happened when the time was equal to 120 minutes

The mass of a marine organism, in pounds, p years after it is born is given by the polynomial function r(p) = -4p2 + 300p. find the mass when p = 20 years.

Since we have computer algebra systems that can solve polynomial division problems for us, why is it necessary to learn how to do these things by hand?