Anne has a broken ruler. it starts at the 3-inch mark and ends at the 12-inch mark. explain how anne could use the ruler to measure the length of a line segment in inches.

The perceived length subtracted by three would give the measure of the length of a line segment. 

x = perceived length
f(x) = actual length

Using this "broken ruler" you would need to use this simple function to get that actual length: 

f(x)= x-3

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