Hancock county social services is preparing materials for a seminar. they purchase a combination of 80 large binders and small binders. the large binders cost $8.49 each and the small ones cost $5.99 each. if the total cost of the binders is $544.20, how many of each size are purchased?

Okay for this problem you would need to use the mid-point formula...
It uses the x and y coordinate system (x , y) 
this is how the formula looks like substitute this for the x coordinate (x₁ + x₂)/2 
and this for the y coordinate (y₁ + y₂)/2

Now all you have to do is substitute the values into the right variables...

E (5 , -2)  is (x₁, y₁)
F (-1 , 3) is (x₂ , y₂)

(x₁ + x₂)/2                          (y₁ + y₂)/2
(5 - 1)/2                             (-2 + 3)/2
4/2                                     1/2
2

We now have the x and y coordinate for the mid-point
The answer is... ( drumroll please :D)  
(2, 1/2)

I hope this helps you! :D

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