What's the answer for p2 when p=25

A33 gram sample of a substance that's used to detect explosives has a k-value of 0.1473. n = noekt no = initial mass (at time t = 0) n = mass at time t k = a positive constant that depends on the substance itself and on the units used to measure time t = time, in days

We just started the introduction into circles and i have no idea how to do this.

Write the expression 7x^3-28xy^2 as the product of 3 factors