Determine mathematically (9)
I believe the answer is:
calculate
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">determine mathematically</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for calculate that I've seen before include "Determine mathematically" , "Compute or reckon" , "Think about" , "'Work out, compute (9)'" , "Work out mathematically" .)