A barrel of oil is 52 kilograms, (1/4) is used, and (79/2) is left. Ask: How many kilograms is the empty barrel?
一桶油52千克，用去(1/4)，还剩(79/2)，问：空桶多少千克？
<gadget id="calculator">79 / 2</gadget>
<output>79/2 = around 39.5</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">52 * (3/4)</gadget>
<output>39</output>

<gadget id="calculator">(79/2) - 39</gadget>
<output>1/2 = around 0.5</output>

<result>1/2 = around 0.5</result>