There are 140 small balls in the sports equipment room of the school, 68 of which are lent out during physical education class, and 45 are returned after class. How many small balls are there in the sports equipment room now?
学校体育器材室有140个小皮球，上体育课时借出68个，下课时还回45个．现在体育器材室有小皮球多少个？
<gadget id="calculator">140 - 68</gadget>
<output>72</output>

<gadget id="calculator">72 + 45</gadget>
<output>117</output>

<result>117</result>