the sum is 17, tess is 5 years older than sam and kia is twice sam's age
Trying to wade through your grammatical gibberish ....
Sam's age --- x
Kia's age = 2x
Tess's age = x + 5
Assuming you imply that the sum of their ages is 17 ....
x + 2x + x + 5 = 17
4x = 12
x = 3
Sam is 3, Kia is 6, and Tess is 8