Which word is used to name the number 2?
x – 2 = 8
a.
difference
b.
factor
c.
minuend
d.
subtrahend

The answer the D. subtrahend.  A subtrahend is the number you subtract from to get the difference, which is the answer.  Factors are a whole other subject, they are the number that is multiplied by to obtain the product.  The minuend is the numbers subtracted from.  
In: x - 2 = 8, x is the minuend, 2 is the subtrahend, and 8 is the difference.