easiest way to solve it is using the equation;
weight to be shifted / total weight = Δcg / distance the weight is shifted
you are trying to work out the difference, which is the Δcg,
Δcg = ( weight to be shifted * distance the weight is shifted ) / total weight
we know the weight to be shifted is 3300 lbs,
the distance to be shifted is from fwd hold (-227.9) to aft hold (144.9), therefore the distance between these two holds is 144.9 plus 227.9, which gives us 372.8,
and the total weight is 88300 lbs.
so now Δcg = ( 3300 * 372.8 ) / 88300
Δcg = 13.93