we have that
−27x2yz5 + 15x3z3
we know that
27-------------> 3³
15-------------> 3*5
z^5-----------> z² * z³
x³------------> x² * x
substituting in the original expression
−27x2yz5 + 15x3z3---------->[-3³*x²*y*z³*z²]+[3*5*x²*x*z³]
[-3³*x²*y*z³*z²]+[3*5*x²*x*z³]-------> [3*x² *z³]*{[-3² *y*z²]+[5*x]}
the greatest common factor is [3*x² *z³]
