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