Hey there! :D
So, we know that there are 3 z's and 3 6's.
3*z= 3z
6*3= 18
3(z+6) <== equivalent expression
3z+18 <== equivalent expression
z is by itself. It shouldn't combine. It should stay the same. 6 as a unit is separate from z.
Choices "B" and "E" are correct.
I hope this helps!
~kaikers