Question

Carrie has recorded her first CD and needs 400 for an upcoming release party. CD Clone charges $150 for 100 CD's and $297 for 250 CD's

Write an equation for the relationship between the numbers of CD's created and the total cost

Book says C=.92d + 67

I'm baffled at how they came up with this answer

Answer 1

$150 for 100 CD's and $297 for 250 CD's

You can realize that the cost will have 2 parts. 1 is independent of the amount of CDs Cloned and the second part is dependent.

So the function C will equal to
C(x)=ax+b (it depends on x, the number of CDs made)

You now can write 2 equations with the 2 data
$150 for 100 CD's

150=100a+b

$297 for 250

297=250a+b

Solve these 2 and luckily you should get the given solution!

Answer 2

Not sure what you mean as you still have 2 variables in each equation

Answer 3

150=100a+b


297=250a+b

2 equations with 2 unknowns.
297-150=250a-100a+b-b
147=150a
a=0.98