a) $325/3 = $108.33
b) You don't tell us what the sales tax % is, so I used 5%.
$x*(1.05) = $325
$x = $325/1.05 = $309.52
$309.52/3 = $103.17
c) Inductive reasoning - going from a specific case (one store out of stock) to a general conclusion (all stores out of stock).
d) What are the 10% and 20% - sales tax? discounts? When writing down your problem statement, be sure to include all necessary information.