Adam could fit 10 action figures on each shelf in his room. His room has could hold 8 action figures. How many total shelves did his room have?
Adam could fit 10 action figures on each shelf in his room. 
That means that if he had one shelf, he could fit 10 action figures on it. 
If he had two shelves, he could fit 20 action figures on them. 
If he had three shelves, he could fit 30 action figures on them. 

We can keep going like this until we find the number of shelves that would allow him to fit 80 action figures. 

If he had eight shelves, he could fit 80 action figures on them. 

So, his room had eight shelves.