Question

What is the remaining credit after 59 minutes of calls

Answer 1

Let's find the equation of the line:

let:

`\begin{gathered} (x1,y1)=(33,15.05) \\ (x2,y2)=(51,12.35) \end{gathered}`

So:

`m=(y2-y1)/(x2-x1)=(12.35-15.05)/(51-33)=-(2.7)/(18)=-0.15`

So:

`\begin{gathered} y-y1=m(x-x1) \\ y-15.05=-0.15(x-33) \\ y-15.05=-0.15x+4.95 \\ y(x)=-0.15x+20 \end{gathered}`

After 59 minutes:

`\begin{gathered} x=59 \\ y(59)=-0.15(59)+20 \\ y(59)=11.15 \end{gathered}`