Answer:
Step-by-step explanation:
 
        
                    
             
        
        
        
The nephew would need to use division to isolate x giving him $66.50 to spend
        
             
        
        
        
Represent 'a number' by x
7 times x equals 9 more than 4 times x
7 times x=9+4 times x
7x=9+4x
subtract 4x from both sides
3x=9
divide 3
x=3
the number is 3
        
             
        
        
        
The state sales tax in Colorado is 2.9%. 
We know that because we divide 2.32/80. We have to find out what percent the tax is of the amount paid. The answer comes to 0.029. Multiply it by 100, and you get 2.9%
 
        
                    
             
        
        
        
The answer to your question is 8.1