Complex sentence: Dyslexia and attention deficit hyperactivity disorder (ADHD) commonly occur together; about 15% of people with dyslexia also have ADHD and 35% of those with ADHD have dyslexia.
Split into simpler sentences: Dyslexia and attention deficit hyperactivity disorder (ADHD) commonly occur together. About 15% of people with dyslexia also have ADHD and 35% of those with ADHD have dyslexia.