(4/19)*((7/10)-((7/15)-(2/5))).
(4/19)*((7/10)-((7/15)-(2/5)))．
<gadget id="calculator">4 / 19</gadget>
<output>4/19 = around 0.210526</output>

<gadget id="calculator">7 / 10</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">7 / 15</gadget>
<output>7/15 = around 0.466667</output>

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

<gadget id="calculator">(7/15) - (2/5)</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(7/10) - (1/15)</gadget>
<output>19/30 = around 0.633333</output>

<gadget id="calculator">(4/19) * (19/30)</gadget>
<output>2/15 = around 0.133333</output>

<result>2/15 = around 0.133333</result>