There are conversion tables everywhere that assist you in changing a different unit into another. Depending on what it is, you can also compare weight into water, cm into m and backwards.
Answer: The red segment is from 1/4 to 3/4. 3/4 - 1/4 = 2/4 2/4 = 1/2 1/2
This answer can also be found by seeing there are four equal boxes making up the one larger box, since two out of the four boxes are filled then the fraction would be 2/4, which simplifies to 1/2
