Hi
Letting x and 4x represent the numbers..good work.
Writing as we Read, important to get the words into a written equation***
product = 4 times their sum
x(4x) = 4(x + 4x) |may be tendency to over think w/o writing while reading
4x^2 -20x = 0
4x(x-5) = 0 x = 0 and x = 5 |tossing out x = 0
x = 5, the other numbers is 20 (4*5)
CHECKING our Answer***
100 = 4*25