Today there are four teenagers A, B, C, and D picking up seeds in the forest. A is the most picked tree seeds, and B, C, and D decrease in turn. The sum of the seeds picked up by A and B is 65, the sum of A and D is 61, and the sum of C and D is 44, so how many seeds does B pick up?
今有A、B、C、D四位少年在森林中拾树籽．拾的树籽数以A为最多，B、C、D依次减少．A和B拾得的树籽数之和为65个，A和D的和为61个，C和D的和为44个，则B拾得的树籽数是多少个．
<gadget id="calculator">21 + 4</gadget>
<output>25</output>

<result>25</result>