A project can be completed by team A alone in 30 days. If team B first works in 7 days, A and B cooperate in 8 days, and the rest of team A will finish in 12 days, how many days will it take for team B to complete it alone?
一项工程，甲队单独做30天完成，若乙队先做7天，甲乙合做8天，其余的甲队再做12天完，乙队独做需多少天完成？
<gadget id="calculator">1 / 30</gadget>
<output>1/30 = around 0.033333</output>

<gadget id="calculator">12 + 8</gadget>
<output>20</output>

<gadget id="calculator">(1/30) * 20</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">7 + 8</gadget>
<output>15</output>

<gadget id="calculator">(1/3) / 15</gadget>
<output>1/45 = around 0.022222</output>

<gadget id="calculator">1 / (1/45)</gadget>
<output>45</output>

<result>45</result>