A piece of chocolate is placed at one end of the balance, and (1/4) piece of chocolate and a weight of 30 grams are placed at the other end. At this time, the balance is just balanced. What is the mass of a piece of chocolate in grams?
天平的一端放着一块巧克力，另一端放着(1/4)块巧克力和30克砝码，此时天平恰好平衡．一块巧克力的质量是多少克．
<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">30 / (3/4)</gadget>
<output>40</output>

<result>40</result>