Answer: An equation we can use to find the number of djembe drums you sold be

Step-by-step explanation:
Let price of maracas be m
Let the price of claves be c
Let the price of djembe drums be d
Number of maracas = 12 sets
Number of clavas = 6 sets
Number of djembe drums be xx
Total earned amount = $326
According to question,

Hence, an equation we can use to find the number of djembe drums you sold be

The axis of symmetry of a parabola in the form

is a vertical line

where k is the x coordinate of the vertex of the parabola.
The x coordinate of the vertex of the parabola is given by

which in your case is

So, the axis of symmetry is the line x=12.
Answer:
D.
Step-by-step explanation:
Expressing something by a unit rate means to express a value per single item. Hence, only D fits (per package, meaning per 1 package.)
Hope this helped!