Please can someone help me with these questions

Which of the following is the missing term, a2, of the geometric sequence in which a1=2 and a3=200

The fence around a quadrilateral-shaped pasture is 3a^2+15a+9 long. three sides of the fence have the following lengths: 5a, 10a-2, a^2-7. what is the length of the fourth side of the fence?

Solve each quadratic equation by factoring and using the zero product property. [tex]x^2+6x+8=0[/tex]