The difference of a number and 9 is the same as the sum of 3 times the number and 12

Step-by-step explanation:

Represent the number as x

Difference of the number and x:

--- (1)

Sum of 3 times the number and 12:

---- (2)

Equate 1 and 2

Collect Like Terms

Make x the subject

x+14

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