Let x be a number of skateboards and y be the number of bicycles in Eddie's repair shop. 
Eddie asks the girls to order 54 new wheels for 21 skateboards and bicycles, then
x+y=21.
One scateboard has 4 wheels, then x scateboards have 4x wheels, one bicycle has 2 wheels, then y bicycles have 2y wheels. In total there should be ordered 54 wheels, so
4x+2y=54.
Solve the system of equations:

From the first equation  Substitute it into the second equation:
 Substitute it into the second equation:

Then

Answer: 6 scateboards and 15 bicycles.
 
        
             
        
        
        
In general, the derivative of a single term  Ax^(n)  is  A n x^(n-1) .
And the derivative of a sum of many terms is the sum of the derivatives 
of the individual terms.   
Using these two rules, the derivative (with respect to 'x') of the expression 
in the question is . . .
<em>            Y' = -21x² - 16x + 6</em>
        
             
        
        
        
Answer:
C
because it is given that the vertex is (4, - 1) an an equation C it is clearly seen that the vertex is same.
 
        
             
        
        
        
Not entirely sure, but it seem the answer could be B.) It will not be spread out vertically across the entire coordinate plane because in step 5, Nancy selected an incorrect scale on the y-axis.