Question 1205552
Not the complete  solution; just an approach:

<pre>
A                   (1/5)(B+C+D)

B                   (1/4)(A+C+D)

C                   (1/2)(A+B+D)

D                         D

TOTAL                      900
</pre>

{{{system(A+B+C+D=900,5A=B+C+D,4B=A+C+D,2C=A+B+D)}}}



Simple linear operations are seeming to show this:
{{{system(6A=900,5B=900,3C=900)}}}

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D gave 30%,