Final answer:
The provided information is fragmented and doesn't lead to a clear solution. Without consistent values of a, b, c, and d, the expression (a+c) - (b+d) cannot be accurately computed. More context or information is needed to solve this question.
Step-by-step explanation:
To calculate (a+c) - (b+d) given that abcx3 = d281, we interpret 'x' as the multiplication sign and 'd' as a variable, we can deduce the values of a, b, c, and d. from the clues given in the various examples. However, as the provided information appears to be fragmented and no clear solution is present in the context provided, it's impossible to accurately compute the answer to the student's question.
Based on the varied information, it seems that different values of a, b, c, and d are offered without a clear way to reconcile them into a single coherent problem. If we are looking at the most complete equation, which is 'abcx3 = d281', there does not appear to be enough information to solve for the individual variables without further context or information.
If any consistent set of values for a, b, c, and d were provided, you would then substitute those values into the expression (a+c) - (b+d) to arrive at your answer.