let

x = the length of the first ribbon, x>0

y = the length of the second ribbon, y>0

they have an unequal length have a ratio of 1.25:2.8

1.25 : 2.8 = x : y

1.25y = 2.8x

and we can assume y>x

The difference between the lengths of ribbons is 85

y - x = 85

by solving the system of equations

1.25y = 2.8x

y - x = 85

to see the step by step solution of the system click here:

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we find the solutions

x = 2125/31

y = 4760/31

the length of the ribbon is

x + y = 2125/31 + 4760/31 = (2125 + 4760)/31 = 6885/31 = 222.097

the length of the original ribbon is 222.097.