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AoPS Wiki:Problem of the Day/June 18, 2011

In trapezoid $ABCD$, $m\angle A=m\angle D=90^{\circ}$. Base $AB$ has a length of $9$ while base $CD$ has a length of $15$. Diagonals $AC$ and $BD$ meet at point $X$. If the perimeter of the trapezoid is $42$, find the distance from $X$ to $CD$.

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