Mental math means calculating the given numbers
without using anything that can help you solve the problem like paper and pen,
calculator, etc.
Now let’s have 81-16
=> 81 -16
=> 65
Now, let’s check if our answer is correct by adding the answer or the
difference by the subtrahend.
By the way in subtraction
81 => minuend
16 => subtrahend
65 => difference