Algebra

The answer is:

\((x-3)(x+16)\)

if you want steps: 

break the expression into groups and then just factor out x in the first part into x(x-3) and then factor the seond part into 16(x-3)

now, rewrite it as x(x-3)=16(x-3)

then, find the lcm (or is it gcf) x-3 and factor that out

finally, we get (x-3)(x+16) which is a binomial, so the answer is reasonable