There is a sales tax $6 on an item that costs $80 before tax. the sales tax on a second item is $11.25. how much does the second item cost before tax?

The answer to this question would be: $138.75

In this question, for item with $80 total price the tax is $6 which mean the actual price (before tax) is $80-$6= $74. 
That mean the ratio of the tax: item= 6:74

Then for the second item, if the tax is $11.25 then the price before tax would be: $11.25* 74/6= $138.75

The discount is 6:80= 7.5%
the second item's price before tax is 11.25:7.5%= (11.25 x 100): 7.5= 150
the answer is $150