Let x be the number of cars. We will find out how many cars you have to wash to make as much money as your friend:
 10x - 25= 13x - 55 Add 25 on both sides and subtract 13x, also both sides:
3x = -30 Now divide both sides by -3:
 x= 10 cars you have to wash.
        
             
        
        
        
Which of the following smallest values
        
             
        
        
        
Answer is 12 to your question
        
                    
             
        
        
        
For the full circle, Area = pi(r)^2
pi x 1^2 = pi 
Semi circle = pi/2 = 1.57 square feet