Dad is 172cm tall, 21cm taller than Xiaohong. How tall is Xiaohong in centimeters? (First write out the quantitative relationship, and then use the equation to solve it)
爸爸身高172厘米，比小红高21厘米．小红身高多少厘米？(先写出数量关系式，再用方程解)
<gadget id="calculator">172 - 21</gadget>
<output>151</output>

<result>151</result>