Answer:
Store C, because the ratio of the number to the cost is 1:6 in store C and 1:7 in store D.
Example:
in store C, 2 shirts divided by $12 = $6 per shirt.
In store D, 3 shirts divided by $21 = $7.
Making the ratios 1:6 (1 shirt: 6 dollars) and 1:7 (1 shirt: 7 dollars)
Explanation: