Which operations is the set of even numbers closed under?

Astrid spent $36 on new shoes. this was $12 less than twice what she spent on a new skirt. part a: which equation would solve for how much she spent on the skirt? part b: solve the equation in the workspace provided below. how much did astrid spend on her skirt?

Afurniture store is having a weekend sale and is offering a 20% discount on patio chairs and tables the sales tax on furniture is 6.25%

Iknow the answer but the calculator doesn't seem to give the right one