copy and paste

I'm coming to Solidworks from Inventor and I've noticed several things that I am having trouble with in solidworks.  The first of which is that there seems to be no easy way to link two dimensions in a sketch.  Just as an example, if I want dimension d6 to be half of d5 in Inventor I could click on dim d6 to edit and then instead of typing in a number I could click on d5 and then type out d5 / 2.  The second is that Ctrl C and Ctrl V pastes the component out in space instead of where I'm clicking my mouse.

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