James decides to start making his own coffee. He buys a coffee machine for $200 and gets a $20 discount. He figures it will cost him $3 a day to make his coffee. He previously bought 2 coffees a day for $4 each.  How long until the machine pays for itself?
Let's be accurate as possible. Think before you answer.
36
He bought the machine for $200 - $20 = $180.

He used to spend 4 * 2 = $8 a day.

So he saves $8 - $3 = $5 a day.

So it will take him $180 / $5 = 36 days to pay for itself.

.

So, the final answer is 36