A piece of iron wire is 80 cm long. How many centimeters of wire are left after making a square with side length 15 cm?
一根铁丝长80厘米，做一个边长是15厘米的正方形后，还剩多少厘米的铁丝．
<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">80 - 60</gadget>
<output>20</output>

<result>20</result>