Let's build the equation counting how many x's and 1's are there on each side.
On the left hand side we have 5x's and 8 1's, for a total of 
On the left hand side we have 3x's and 10 1's, for a total of 
So, the equation we want to solve is

Subtract 3x from both sides:

Subtract 8 from both sides:

Divide both sides by 2:

Answer:
2/3
Step-by-step explanation:
-2 and 4 are 6 away
4 and 13 are 9 away
Thus it is 6/9 or 2/3
But it's not one doesn't always have to be the gcf
Answer:
C - 10
Step-by-step explanation:
n is the number of the term
an = -2n+8
a9 = -2*9 +8
a9 = -18+8
a9 = -10
The 9th term is -10