When Tang Le copied English words, the ratio of the completed number to the total number to be copied was 1:3. If 15 words are copied, then the completed number is as many as the remaining ones. How many English words does Tang Le want to copy?
唐乐抄英语单词，已完成的个数与要抄的总个数的比是1：3．如果抄写15个，那么完成个数与剩下的个数同样多，唐乐要抄的英语单词共有多少个？
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + 3</gadget>
<output>4</output>

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

<gadget id="calculator">(1/2) - (1/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">15 / (1/4)</gadget>
<output>60</output>

<result>60</result>