Answer: The variables are the Cost of the item, and the Total cost.
The other cost, the shipping is given here: $2. So that is not really a variable.
You can use almost any letters you'd like. I'm using C for the item's cost, and T for the total cost in this equation:
C + 2 = T
This question seems to imply that only one item is in the order
Explanation:
There may be other ways to do this, if multiple items are ordered.
The variables are the Cost of the item-- and how Many items are purchased.
The Total is also a variable that depends on how many and the cost of the items.
The other cost, the shipping might be a variable in other questions (not here) here: S could be a variable if it is a percentage ot the cost.
You can use almost any letters you'd like. I'm using C for the item's cost, M for the number of items, S for variable shipping, and T for the total cost in this equation:
M×C + S = T