Question

a store sells new DVDs for $12 each. used DVDs sell for $7 each. Joseph is buying two new DVDs and X used DVDs. write an equation that can be used to find X, the total Joseph must pay in dollars

Answer 1

Given that new DVDs are selling for $12 and used for $7, then Joseph is buying:
12·2 + 7x = 

Answer 2

Used DVDs = x
Total = t

t = 12(2) + 7x
t = 24 + 7x
t - 24 = 7x 
(t - 24) / (7) = x

If given the total, you can plug it in to variable t and then work the right side of the equation to isolate variable x and solve to find its value.