The sum of twice a number and (4/5) is (8/5). What is this number?
一个数的2倍与(4/5)的和是(8/5)．这个数是多少？
<gadget id="calculator">8 / 5</gadget>
<output>8/5 = around 1.6</output>

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

<gadget id="calculator">(8/5) - (4/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(4/5) / 2</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>