Answer:
65 See below
Explanation:
when doing mental math you need to break it apart to more manageable chunks.
I would think of this as 70 and 11 - 6 = 75 then subtract 10 = 65
we have
(81-16)
One way to use mental math is to add 4 to both 81 and 16
so
81+4=85\\ 16+4=20\\ 85-20=65
therefore
81-16=65
the answer is
65
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