Let $T_W$ be the temperature on the W scale and $T_C$ be the temperature on the Celsius scale. For any two linear temperature scales, the ratio of the difference between any temperature and the lower fixed point (freezing point) to the fundamental interval (difference between boiling and freezing points) is constant. $\frac{T_W - \text{LFP}_W}{\text{UFP}_W - \text{LFP}_W} = \frac{T_C - \text{LFP}_C}{\text{UFP}_C - \text{LFP}_C}$ Given: $\text{LFP}_W = 39^{\circ}\text{W}$, $\text{UFP}_W = 239^{\circ}\text{W}$ $\text{LFP}_C = 0^{\circ}\text{C}$, $\text{UFP}_C = 100^{\circ}\text{C}$ $T_C = 39^{\circ}\text{C}$ Substituting the values: $\frac{T_W - 39}{239 - 39} = \frac{39 - 0}{100 - 0}$ $\frac{T_W - 39}{200} = \frac{39}{100}$ $T_W - 39 = 39 \times \frac{200}{100}$ $T_W - 39 = 78$ $T_W = 78 + 39 = 117^{\circ}\text{W}$