What is the approximate dew point temperature if the bulb temperature is 11 degrees C and the wet- bulb temperature is 8 degrees C?
5 C aprox.
In weather observing we use a table and not the actual formulas. Converting the wet bulb to relative humidity (RH) we get 66%. 66% RH at 11 C is about 5 C.
Here is a picture of a table for converting wet bulb to dew point. You take the air temperature on the left and look at the difference between the dry bulb and wet bulb at the top ( in this case 3). This is a good approximation not an exact value.