(16x^2+4x-4x-1)-3=15x^2
16x^2-1-3=15x^2
16x^2-4=15x^2
X^2=4
X=+or-2
Mean is 27.4
Median is 22
Range is 27
Just use the mathematical definition of each word
A geometric figure enclosed by a circle is called an inscribed figure.
For this case we have to:
x: It is the variable that represents the number of compact discs.
The cost function must be found considering that each disk costs $7.13. So:

Thus, to find the total cost of "x" compact discs (in $) we substitute the number of discs in the cost function.
Answer:

0.6x + 1.5 = 3.9
0.6x = 3.9 - 1.5
0.6x = 2.4
x = 2.4 ÷ 0.6
x = 4