Dan has $ 16. He bought some candy bar for $ 4 each one costing $ 4. How many candy bar did he buy?
Dan has $16. 
He buys candy bars for $4 each. 
That means that each candy bar costs $4. 

Now we can set up an equation: 

16 = 4x 

We can solve for x by dividing both sides by 4: 

16/4 = 4x/4 

4 = x 

That means that Dan bought 4 candy bars.