Divide 12 on both sides
ds/w=cd/12
now multiply ds on both sides
w=cd/12ds
Let 
be the length of a leg. Using the pythagorean theorem, the hypotenuse is
So, the hypotenuse is 
times as long as either leg.
You didn't supply a list. The so-called rigid transformations of translation, rotation and reflection create congruent triangles.
Generally it's dilation by a factor about a point is preserves similarity but not congruency. Any transformation which includes such scalings but is otherwise rigid also preserves similarity but not congruency.
