4.5/(((1/2)-3/7.5)*(3/5)).
4.5/(((1/2)-3/7.5)*(3/5))．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">3 / 7.5</gadget>
<output>0.4</output>

<gadget id="calculator">(1/2) - 0.4</gadget>
<output>0.1</output>

<gadget id="calculator">3 / 5</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">0.1 * (3/5)</gadget>
<output>0.06</output>

<gadget id="calculator">4.5 / 0.06</gadget>
<output>75</output>

<result>75</result>