Could someone me with this math problem

The easiest way to do this is to draw a blob where you need to end up and basically connect the origin (0,0) to the dot (or if there are changes, connect each of the dots in turn).

The difference between 11am and 2pm is 3 hours, so we will be going up to 3 on the x axis.
In this time he has travelled 12 kilometres, therefore we will go up to 12 on the y axis.
Putting this together, draw a dot at (3,12).
Now, draw a straight line from (0,0) to (3,12) - this is your line.

The slope of the line represents distance/time, i.e. how far he covered per unit time, which translates in layman's terms to speed i.e. how fast the hiker was going.