human
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?
assistant
How much did the machine cost? ** He bought the machine for $200-$20=$<<200-20=180>>180
How much did James spend on coffee? ** He used to spend 4*2=$<<4*2=8>>8 a day
How much does James save? ** So he saves $8-$3=$<<8-3=5>>5 a day
How long will it take the machine to pay for itself? ** So it will take him $180/$5=<<180/5=36>>36 days to pay for itself
#### 36