Make a line 5 inches (or cm) long, put an arrow on one end, and label it “train”.

From the arrow head, draw another arrow-line BACK across the page. Make it 2 inches (or cm) long, and label it “me”

Does that help? As Albert Einstein would say, its all relative.

Compared to the rest of the train, you are moving Backwards at 2 mph. You said so yourself!

BUT- compared to the Outside World? If you look through a train window, or at your arrow drawing, you are still moving forward- just not as fast as the train. You are moving forward at a steady 3mph.

the train is moving 5 mph in one direction, but you are walking 2 mph in the other direction. 5-2=3

This is the simplest of answers; however, speed requires a frame of reference. You are moving 3 mph relative to the ground, but you are moving 2 mph relative to the train. You are not moving relative to the train conductor walking behind you at 2 mph, and you are moving 4 mph relaitve to the kid walking to the front of the train at 2 mph. Relative to the bird passing the train at 20 mph, you are moving 22 mph.

or so it would seem

The train is moving forward 5 miles [why is it going so fluffin slow anyway?]

Your moving the opposite direction 2 miles.

Since your moving 2 miles in the opposite direction, that will add negative force to the train speed towards you making you moving 3miles i think.

Good Luck!