A box containing 15 DVDs is selling for $156.00. The box contains some DVDs worth $11.00 each and some DVDs worth $9.00 each. Which system of

equations can be used to determine x, the number of $11.00 DVDs, and y, the

number of $9.00 DVDs?

Step-by-step explanation:

x + y = 15

11x + 9y = 156

answer: the first graph

step-by-step explanation:

answer: 204

step-by-step explanation:

we are told that the revenue is

x⋅(4080−10x)=−10x^2+4080x

this is a quadratic function, so to maximize it we should find the x-value of its vertex. recall that the x-value of the vertex of the parabola ax^2+bx+c is given by the formula −b/2a.

so in this case, we have a=−10 and b=4080, so the x-value of the vertex is

−b/2a= −(4080)/2(−10)=204