Cassie has 10 cousins. There is only 1 Jackson cousin,but there are twice as many Lopez cousins as Chen cousins. How many Lopez cousins does she have

Given:
10 cousins
1 Jackson cousin
twice as many Lopez cousin as Chen cousin.

The unknown are the number of Lopez cousin and Chen cousin. 

Let x represent the number of Chen cousin. Since Lopez cousin is twice the number of Chen cousin, the Lopez cousin is represented by 2x.

1 + 2x + x = 10
3x = 10 - 1
3x = 9
x = 9/3
x = 3 → Number of Chen cousins

2x → 2(3) = 6 → Number of Lopez cousins

There is 1 Jackson cousin, 6 Lopez cousins, and 3 Chen cousins. For a total of 10 cousins.