She paid 42.00 dollars for the vase.
Work Step by Step
Marci sold the vase for 15 dollars less than twice the amount she paid for it. Let X represent the price she paid for the vase. Since she paid X for the vase, twice the amount she paid for it means 2 $\times$ X = 2X 15 less than twice the amount she paid for it means 2X - 15. Since we know that Marci sold the antique vase for 69.00 dollars, we obtain: 2X - 15 = 69.00 Add 15 to both sides 2X = 84.00 Divide both sides by 2 X = 42.00