There are 9 people in a transportation squad. If everyone carries the same number of helmets, they can carry all the helmets on their backs. Later, 2 people were added, but one of them was lazy and missed 2 helmets. The rest of the soldiers carried 2 helmets each. The number of helmets remains the same, so a total of 10 more helmets are carried than before. May I ask: How many steel helmets did the whole class carry at the beginning?
一个运输班有9个人，如果每个人背的钢盔数都相同，正好能够把全部钢盔背上；后来增加了2个人，但是有一个偷懒少背了2个钢盔，剩下的士兵每人背的钢盔个数不变，这样一共比原来多背了10个钢盔．请问：开始全班一共背了多少个钢盔？
<gadget id="calculator">10 + 2</gadget>
<output>12</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">6 * 9</gadget>
<output>54</output>

<result>54</result>