There are 85 cows in a cattle farm, and each cow eats 9 kg of grass every day. The cattle farm transports 900kg of grass every day, how many kilograms of grass are left after eating?
养牛场有85头奶牛，每天每头吃9千克草．养牛场每天运来900kg草，吃完后还剩多少千克草？
<gadget id="calculator">9 * 85</gadget>
<output>765</output>

<gadget id="calculator">900 - 765</gadget>
<output>135</output>

<result>135</result>