A and B both bought milk powder with the same amount of money. A takes 12 bags and B takes 9 bags. After returning home, A returns B 7.2 yuan. How much is each bag of milk powder?
甲、乙两带着相同数量的钱全部买了奶粉．甲拿去12袋，乙拿去9袋，回家后，甲还给乙7.2元．每袋奶粉多少钱？
<gadget id="calculator">7.2 + 7.2</gadget>
<output>14.4</output>

<gadget id="calculator">12 - 9</gadget>
<output>3</output>

<gadget id="calculator">14.4 / 3</gadget>
<output>4.8</output>

<result>4.8</result>