now, let's say you have only $20 in your pocket right now. you're on an extremely tight budget. that $12 is inclusive of your bus/train fares. let's say, you're staying in tampines and your destination is to go to yishun, that's 1 bus ride away, and that will cost you $1.20, it's cheap comparing if you're taking a taxi, that'd cost you $12, you'd save $7.80. Ok, with the amount of money left, you go and but a happy meal instead of an extra value meal. A happy meal will cost you $4.50 and an EVM will cost you $7. You'd save $1.50. On the way home, you took a train, you'd have to pay $2.80 first but they would return you that $1 once you reached your hometown and only if you returned that green ticket as well, thus only making you pay$1.70 only for the train ride.
You come back home and you realized that you still have some cash. 4 $2 notes and 2 $5 note.

Now, moral of the story- I can't count.

Good night.