Jinnan District has to transport 200 tons of relief materials to the Wenchuan earthquake-stricken area, 40% of the total is transported in the first time, and 50 tons in the second time. How many tons of disaster relief materials are left waiting to be transported?
津南区要为汶川地震灾区运送200吨救灾物资，第一次运走总数的40%，第二次运走50吨，还剩下多少吨救灾物资等待运走？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">200 * (2/5)</gadget>
<output>80</output>

<gadget id="calculator">200 - 80 - 50</gadget>
<output>70</output>

<result>70</result>