There is a digital video camera, and the image quality is divided into three categories: best, good, and average. It is equipped with a memory card that can store up to 120 best photos, or 160 good photos, or 280 general photos. Now there are 30 best photos and 60 good photos in this memory card, so how many ordinary photos can be stored?
有一台数码摄像机，成像质量分为最好、好、一般三种．它配得一种储存卡最多可以储存最好的120张，或储存好的照片160张，或储存一般的照片280张．现在这张储存卡中有最好的照片30张，好的照片60张，那么还能存一般的照片多少张？
<gadget id="calculator">30 / 120</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">60 / 160</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">1 - (1/4) - (3/8)</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">280 * (3/8)</gadget>
<output>105</output>

<result>105</result>