Final answer:
Crystal has 4,000 followers based on the equation x + 2x = 12,000, where x represents Crystal's followers and 2x represents Vanessa's followers.
Step-by-step explanation:
To determine how many followers Crystal has, we can set up an equation where x represents the number of followers that Crystal has. Since Vanessa has twice the number of followers that Crystal has, we denote Vanessa's followers as 2x. The problem states that together they have 12,000 followers.
The equation to represent this situation is:
x + 2x = 12,000
3x = 12,000
x = 12,000 / 3
x = 4,000
Therefore, Crystal has 4,000 followers, and Vanessa, having twice as many, has 8,000 followers.