A technology book costs 2 yuan and 30 cents, which is 80 cents and 5 cents cheaper than a story book. How much is a story book? (calculated with decimals)
一本科技书2元3角，比一本故事书便宜8角5分，一本故事书多少元？(用小数计算)
<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">2 + (3/10)</gadget>
<output>23/10 = around 2.3</output>

<gadget id="calculator">(23/10) + 0.85</gadget>
<output>3.15</output>

<result>3.15</result>