REPEAT FirstRepeat
SET SecondVar[COUNTER] TO FirstVar
END REPEAT
Alternative:
REPEAT FirstRepeat
DEFAULT SecondVar[COUNTER] TO FirstVar
END REPEAT
REPEAT SecondRepeat
SecondVar
END REPEAT
The computation steps through the first repeated variable, copying each of its answers to the second variable. COUNTER tells the computation which answer to set. For example, the first pass will give FirstVar's answer #1, or FirstVar[1], to SecondVar[1]. The second pass will set SecondVar[2], etc.
The Alternative uses DEFAULT instead of SET. This allows you to still change the second variable's answers if you want to.