Respuesta :

Let Jill be x years old
Jill = x 
Jack = 10x

16 years later ...
Jill = x + 16
Jack = 10x  + 16 

Jack is twice as old as Jill ...
jack = 2 x Jill

10x + 16 = 2 (x + 16)
10x + 16 = 2x + 32
10x - 2x = 32 - 16
8x = 16
x = 2

Jill = 2 years old
Jack = 20 years old