Roughly 3,07% of the houses are priced over $300 000
"Suppose that 3.5% of the houses in the area get a property tax exemption due to their low values. Find the value above which households are not qualified for the exemption?"
So of a certain value must give you 0,035
To get that value, use your standard normal table in "reverse".
My table is more inaccurate since it has less decimal places than the average table. So recheck it.