There are two tasks, A and B. Xiao Li needs 10 days to complete A alone, and 15 days to complete B alone; Xiao Zhang needs 7 days to complete A alone, and 25 days to complete B alone. If every If two people can work together on any task, how many days will it take to complete both tasks A and B?
有甲、乙两项工作，小李独做甲工作需要10天完成，独做乙工作需要15天完成；小张独做甲工作需要7天完成，独做乙工作需要25天完成，如果每项工作都可以由两人合作，那么甲、乙两项工作都完成时最少需要多少天？
<gadget id="calculator">7 / 1</gadget>
<output>7</output>

<gadget id="calculator">1 / 15</gadget>
<output>1/15 = around 0.066667</output>

<gadget id="calculator">(1/15) * 7</gadget>
<output>7/15 = around 0.466667</output>

<gadget id="calculator">1 - (7/15)</gadget>
<output>8/15 = around 0.533333</output>

<gadget id="calculator">1 / 25</gadget>
<output>1/25 = around 0.04</output>

<gadget id="calculator">(1/15) + (1/25)</gadget>
<output>8/75 = around 0.106667</output>

<gadget id="calculator">(8/15) / (8/75)</gadget>
<output>5</output>

<gadget id="calculator">7 + 5</gadget>
<output>12</output>

<result>12</result>