The students eat bread for breakfast, and there are 10 pieces of bread in each bag. At the beginning, 9 students came. After the teacher distributed the same number of slices of bread to each of them, there was still half a bag left. Later, 5 more students came, and the teacher found that he had to buy two more bags of bread to distribute the same amount of bread to each of the new students. Q: How many bags of bread did the teacher prepare at the beginning?
同学们早餐吃面包，每袋面包有10片，开始来了9个同学，老师给每人发了同样多片面包之后，还剩下半袋．后来又来了5个同学，老师发现还要再买两袋面包才够给新来的同学每人发同样多的面包．问：老师开始准备了几袋面包？
<gadget id="calculator">10 / 2</gadget>
<output>5</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<gadget id="calculator">5 + 20</gadget>
<output>25</output>

<gadget id="calculator">25 / 5</gadget>
<output>5</output>

<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">5 * (9/10)</gadget>
<output>9/2 = around 4.5</output>

<gadget id="calculator">(9/2) + 0.5</gadget>
<output>5</output>

<result>5</result>