You can make 6 different towers. If red was at the bottom, there'd be two different possibilities for that: red, yellow, blue, and red, blue, yellow. Same for if blue was at the bottom: blue, red, yellow, and blue, yellow, red. Yellow also applies: yellow, red, blue, and yellow, blue, red. 3*2=6, so 6 possible towers. 
        
             
        
        
        
Answer:
See Below
Step-by-step explanation:
1) 180 ft / 6 sec
To find a unit rate, you need to have a denominator of 1 and to to do that, you can divide the numerator and denominator by the same number, in this case: 6.
30 ft / 1 sec
2) 86 mi / 5 hr
Same as above^(except dividing by 5)
17.2 mi / 1 hr
3) 83 mi / 5 hr
Same as above^^
16.6 mi / 1 hr
We can rewrite this as: 16.6 mph
4) 93 mi / 5 hr
Same as above^^^
18.6 mi / 1 hr
5) 150 mi / 4 hr
Same as above^^^^
37.5 mi / 1 hr
We can rewrite this as: 37.5 mph
 
        
                    
             
        
        
        
Answer:
You should evaluate whatever is in the parenthesis first.