Answer: The required value is \(6c-d.\)
Step-by-step explanation: We are given to find the following :
\(a-2b+3c\) diminished by \(a-2b-3c+d.\)
We know that
the expression p diminished by q is written as "p - q".
Therefore, the given expression implies
\(a-2b+3c~\textup{diminished by}~a-2b-3c+d\\\\=(a-2b+3c)-(a-2b-3c+d)\\\\=a-2b+3c-a+2b+3c-d\\\\=6c-d.\)
Thus, the required value is \(6c-d.\)