Answer:
40 copies for $3000
Step-by-step explanation:
First: The Equation
y=(20+x)(100-x)
This shows how for every new painting, the price will go down.
y=2000+80x-x²
Convert it to standard form: ax²+bx+c
You can now choose to graph it or find the vertex form. For the limit of time, I will just use a graph.
The vertex, (40,3000), is your answer, where the x value is the number of paintings and the y value the money made.
3/4-7/9+2/3=0.63
.........
Answer: The last one
Step-by-step explanation: The data is all between 4 and 7 and there are no gaps. The max is 7 dollars as stated.