A certain number (4/9) is 2.1 more than 1.8 (5/6), what is this number?
某数的(4/9)比1.8的(5/6)多2.1，这个数是多少？
<gadget id="calculator">5 / 6</gadget>
<output>5/6 = around 0.833333</output>

<gadget id="calculator">1.8 * (5/6)</gadget>
<output>1.5</output>

<gadget id="calculator">1.5 + 2.1</gadget>
<output>3.6</output>

<gadget id="calculator">4 / 9</gadget>
<output>4/9 = around 0.444444</output>

<gadget id="calculator">3.6 / (4/9)</gadget>
<output>8.1</output>

<result>8.1</result>