The question says

Question

The question says 
When the square of a certain number is diminished by 5 times.. 
What does diminished by mean?

Steve · Answer

reduced.

Actually, there is a link to the parts of a subtraction problem. In words, we have

minuend
- subtrahend
----------------
difference

That is, the minuend is diminished by the amount _{subtracted (the subtrahend), yielding the difference.

*sigh* it seems folks have lost the ability to just pick up a dictionary any more ... It would have been much faster than posting such a question and waiting for any replies.}