The sales tax rate in jans town is 7.5.if she buys 3 lamps for $23.59 each and a sofa for $769.99 , how much sales tax does she own ?

I believe that tax rate are in percent, so tax rate = 7.5%

Now, lets we total the money that she must pay without tax ( just for 3 lamps and 1 sofa ) :
3 lamps = 3 . $23.59 = $70.77
1 sofa = $ 769.99
Total amount = $769.99 + $70.77 = $840.76

We have to find tax amount, the tax amount of the total amount is about 7.5% of the price. Then we have to adding the tax amount into the total amount. So that we have the Total amount including the tax.

tax amount = 7.5% . 840.76 = $63.057
Total amount (inc. tax amount) =
$840.76 + $63.057 = $903.817

Therefore, she must pay those sofa and lamps about $903.817. So expensive huh? =))