x*5/3*9+11=1991, x=how much.
x*5/3*9+11=1991，x=多少．
<gadget id="calculator">1_991 - 11</gadget>
<output>1_980</output>

<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">(5/3) * 9</gadget>
<output>15</output>

<gadget id="calculator">1_980 / 15</gadget>
<output>132</output>

<result>132</result>