Given
Tax rate = 28.5 mills
Smith's house is accessed at $80,000
Jones's house is accessed at $67,000
Property taxes are calculated by multiplying the assessed, taxable property value by the mill rate and then dividing that sum by 1,000.
The formula is given by:

Property tax for the Smith's:

Property tax for the Jones':

The extra amount the Smith's pay is the difference in the tax levied on Smith and Jones:

Hence, the Smith's pay $370.5 more than the Jones'