Xiaoling asked a grandpa how old he is this year, and the grandpa said: "add 17 to my age and divide by 4, then subtract 15 and multiply by 10, it is exactly 100 years old." So, how old is this grandpa this year? ．
小玲问一老爷爷今年多大年龄，老爷爷说："把我的年龄加上17后用4除，再减去15后用10乘，恰好是100岁"那么，这位老爷爷今年多少岁．
<gadget id="calculator">100 / 10</gadget>
<output>10</output>

<gadget id="calculator">10 + 15</gadget>
<output>25</output>

<gadget id="calculator">25 * 4</gadget>
<output>100</output>

<gadget id="calculator">100 - 17</gadget>
<output>83</output>

<result>83</result>