Mom gave Xiaohua 20 yuan. She bought a pen for 5 yuan and 6 cents, bought study materials for 7 yuan and 5 cents, and bought exercise books for 4 yuan and 8 cents. How much money is left? (calculated with decimals)
妈妈给小华20元钱，她买钢笔用去5元6角，买学习资料用去7元5角，买练习本用去4元8角，还剩多少元？(用小数计算)
<gadget id="calculator">6 / 10</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">5 + (3/5)</gadget>
<output>28/5 = around 5.6</output>

<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">7 + (1/2)</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">8 / 10</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">4 + (4/5)</gadget>
<output>24/5 = around 4.8</output>

<gadget id="calculator">(28/5) + (15/2) + (24/5)</gadget>
<output>179/10 = around 17.9</output>

<gadget id="calculator">20 - (179/10)</gadget>
<output>21/10 = around 2.1</output>

<result>21/10 = around 2.1</result>