You can put this solution on YOUR website! 14.31 minus blank = 11.43
What number must be taken from 14.31 to get an answer of 11.43. As 11.43 + 2.88 = 14.31 then the blank must be 2.88.
(Alternatively try taking 11.43 from the 14.31. This also gives the answer of 2.88)