In the days of earthquake relief, Uncle Zhang of the PLA fought for 74 hours on the front line in the first 4 days, and worked on the front line for an average of 15 hours a day in the next 3 days. How many hours did Uncle Zhang work on the front line on average this week?
在抗震救灾的日子里，解放军张叔叔前4天在一线共奋战了74小时，后3天平均每天在一线工作15小时，这一周，张叔叔平均每天在一线工作多少小时？
<gadget id="calculator">15 * 3</gadget>
<output>45</output>

<gadget id="calculator">74 + 45</gadget>
<output>119</output>

<gadget id="calculator">4 + 3</gadget>
<output>7</output>

<gadget id="calculator">119 / 7</gadget>
<output>17</output>

<result>17</result>