4 days I have 140 copies of a book, 9 days I only have 50 left. Write an equation where c(t)=my+b where c is number of copies still on hand and t days being available.

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Step-by-step explanation:

We have been given that 4 days I have 140 copies of a book, 9 days I only have 50 left. We are asked to write an equation , where c is number of copies still on hand and t days being available.

We have two points on line (4,140) and (9,50). Now, we will use these points to find slope as:

Now, we will use point-slope form of equation and substitute and coordinates of point (9,50) as:

Therefore, our required equation would be .