Xiao Ming said that this year his age is 3 years younger than his grandfather's (2/7). It is known that Xiao Ming is 15 years old this year, how old is grandpa?
小明说，今年他的年龄比爷爷的(2/7)还小3岁．已知小明今年15岁，爷爷今年多少岁？
<gadget id="calculator">15 + 3</gadget>
<output>18</output>

<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">18 / (2/7)</gadget>
<output>63</output>

<result>63</result>