Three boxes, first box has 12 pens for $25, second box has 50 pens for X cost and the third one has 100 pens for $175 . the cost for pens decreases as increase the number of pens . what the cost for the second box?

Answer 1

assume a linear relation. Then you need a constant slope to the function:

(x-25)/(50-12) = (175-x)/(100-50)
or
25/12 - x/50 = x/50 - 175/100

depending on how you are defining the decrease