Dan has $ 13. He bought a chocolate for $ 31 and a candy bar for $ 2. How much money did he spend to buy chocolate than he did to buy candy bar?
Dan has $13. 
He buys a chocolate for $3. 
This leaves him with $10. 
He buys a candy bar for $2. 
This leaves him with $8. 

So, Dan spent $5 more on chocolate than he did on candy bars.