((1/4)-(1/7))*28.
((1/4)-(1/7))*28．
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(1/4) - (1/7)</gadget>
<output>3/28 = around 0.107143</output>

<gadget id="calculator">(3/28) * 28</gadget>
<output>3</output>

<result>3</result>