Factor the polynomial by its greatest common monomial factor 12k^3-30k^4

Hi my sisters and brothers can tell me the answer because i don’t understand the question

The lengths of two sides of a right triangle are given. find the length of the third side. round to the nearest tenth if necessary. a) y = 12/5x + 39/5 b) y = 5/12x + 5/39 c) y = 12/5x - 39/5 d) y = 5/12x - 5/39

Can some one me with these questions