Answer:
The maximum number of minutes to keep the cost at $50 or less is 110 minutes
Step-by-step explanation:
Given
[tex]C(x) = 30[/tex] ---- [tex]x < 60[/tex]
[tex]C(x) = 30 + 0.40(x - 60)[/tex] --- [tex]x \ge 60[/tex]
Required
[tex]C(x) = 50[/tex] ---- find x
We have:
[tex]C(x) = 30 + 0.40(x - 60)[/tex]
Substitute 50 for C(x)
[tex]50 = 30 + 0.40(x - 60)[/tex]
Subtract 30 from both sides
[tex]20 = 0.40(x - 60)[/tex]
Divide both sides by 0.40
[tex]50 = x - 60[/tex]
Add 60 to both sides
[tex]110 = x[/tex]
[tex]x =110[/tex]