After one year its value is (100-12)% of what it was at the start of the year
So you can find 88% of $10,000 by doing 0.88x10,000
and 88% of that is 0.88 x your answer
and 88% of that is 0.88 x your answer.
To do it in one quick easy calculation work out 0.88^3 x 10000