The sequence multiplies by 1/3.
Using the formula for a geometric sequence:
a(n) = a(1) * r^(n-1)
So...
a(n) = 648 * (1/3)^(n-1)
Plugging in 8 for n produces:
a(n) = 648 * (1/3)^(7)
Using a calculator, I find the answer to be 0.296296296...
-2(x-6)+7=35
-2x+6+7=35 (Distributive property)
-2x+13=35 (Simplify, combine like terms)
-2x+13-13=35-13
-2x=22
-2x/-2=22/-2
X=-11