Answer
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
