Answer
-3.75$^{\circ}$ O
Work Step by Step
First, you need to calculate how many degrees C is 1 degree O. The problem states that the freezing point of Oleic acid will be set as 0$^{\circ}$ O while the boiling point of Oleic acid will be set as 100$^{\circ}$ O. Since in Celsius, the freezing point is 13$^{\circ}$C and the boiling point is 360$^{\circ}$C, take the difference of 360 and 13 and divide it by 100$^{\circ}$C. This gives you and equivalence of 1$^{\circ}$O is 3.47$^{\circ}$C. This means that 13$^{\circ}$C is the equivalent of approximately 3.75$^{\circ}$O. And since the new "0" is at 13$^{\circ}$C, that means that the new freezing point of water has been lowered by 13$^{\circ}$C or 3.75$^{\circ}$O to -3.75$^{\circ}$O.
