Question Regarding Time Passage @ Light Speed

[Austellio]

Homework Statement

"Anthony and Dobson are twins. Dobson travels in a straight line away from Earth for 7 years according to his time at 0.96 times the speed of light. After 7 years he turns back and travels back to Earth at half the speed. Meanwhile, Anthony was waiting stationary on Earth. When Dobson gets back, what is the age difference in years between Anthony and Dobson ?"

Homework Equations

The Attempt at a Solution

None =\ very much confused on this extra credit question.

A couple bucks via PayPal if anyone can help me figure this out. I don't want just an answer, but help understanding the math behind the answer.

 

[borgwal]

Ever heard of time dilation?

 

[Austellio]

I am familiar with the concept but as far as the math behind it, I'm completely clueless. Been reading everything I could get my hands on, it's making me feel real stupid >.<

 

[borgwal]

http://en.wikipedia.org/wiki/Time_dilation