Please help me with the following algebra problems

1. What is the GCF of 12x²yz³, 16x²y², 20x²z²?

2.What is the GCF that can be factored out of each monomial term in 6x²-18x+15?

3. What value is needed to fill in the blank to make this trinomial a perfect square trinomial. 4x² + __x + 81?

7.Which of the following is a factor of 2x²-18?

A. x+3

B. x-9

C. x+9

D. 2x-3

11. Which of the following is a factor of 4x²-25?

A. 2x+5

B. x-5

C. x+5

D. 2x-1