So every 5 inches in height, there are 32 marbles. You want to know how many marbles there are per 18 inches in height. 

To get from 5 to 18, you multiply by 3.6. 
Do the same thing to the numerator; 32 × 3.6 = 115.2. 
Since 0.2 marbles is no marbles, you round down. 
There are 115 marbles in the box. 
♡ Hope this helps! ♡ 
 
❀ 0ranges ❀