For a piece of land, use it for cabbage (4/15), use it for radish (7/15), and use the rest for green vegetables. How much of this land is used for growing vegetables?
一块地，种白菜用去它的(4/15)，种萝卜用去它的(7/15)，其余的种青菜．种青菜用去这块地的几分之几？
<gadget id="calculator">4 / 15</gadget>
<output>4/15 = around 0.266667</output>

<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">1 - (4/15) - (7/15)</gadget>
<output>4/15 = around 0.266667</output>

<result>4/15 = around 0.266667</result>