Please need help solving problem (line chart)

Hi all, I was wondering if someone can be kind enough to help explain to me how I would go about solving this question. Its been a very long time since I did maths of this level and am pretty sure for most of you its as basic as you can get but if someone can explain to me how you came up with the answer that would be fantastic and I would be extremely grateful.

The Graph shows the distance travelled by a MotorCycle and a Car during a day. How far in total does the MotorCycle Travel?

http://www.fdmacademy.com/meshcms/ad...kegraph001.gif

The answer is 80km but how do I work something out like this?

Thanks for comments and suggestions. Regards, Onam.