You can
put this solution on YOUR website!10 is not a factor of 16 or 72. Also the first term only has one z.
You need to find a common factor of all. Start by listing all the factor of 16, 40 and 72.And then see what variables they have in common and make sure the same number is in all.

16 = 1,2,4,8,16

= x, x
z = z

40 = 1,2,4,5,8,10,20,40
x = x

= z , z

72 = 1,2,3,4,6,8,9,12,18,24,36,72

=z,z,z
Now list what is the greatest common of all.
:)