For this specific equation we have to use something called factor by grouping to simplify the equation. This is done by using like terms. To began ill break the equation into two groups.
i) (1)12x^3-60x^2
(2) 4x-20
ii) Now we look for like terms and simplify
(1) 12x^2(x-5)
(2) 4(x-5)
iii) Now we put them back as they were in the equation
12x^2(x-5) + 4(x-5)
iv) Now the x-5 factors out
we have (x-5)(12x^2+4)
Lasty, we simplify it to:
(x-5)4(3x^2+1) or 4(3x2 + 1)(x-5)
The last choice given in the answer bank.
Hope this helps, good luck.