a) The total cost of Lisa's purchase was 2x. The individual cost of Dave's purchase was (x-3.50), so his total cost was 4(x-3.50). These costs were equal, so an approriate equation is
... 2x = 4(x -3.50)
b) Eliminate parentheses, subtract 2x, divide by 2.
... 2x = 4x -14.00
... 0 = 2x -14.00
... 0 = x - 7.00
Add 7 to show the value of x
... 7.00 = x
c) Lisa's total purchase was 2x = 14.00. Dave's items cost 7.00 -3.50 = 3.50 each, and the 4 of them came to 4×$3.50 = $14.00, the same as Lisa's total.
d) The cost of one of Lisa's shirts was $7.00; the cost of one of Daves shorts was $3.50.
