Question

m + 5/2m2 - 7m + 5 - 5/2m3

Answer 1

Let me see if I understand the problem:
\[m+(5/2)m ^{2}-7m+5-(5/2)m ^{3}\]
Is that what you are trying to simplify?

Answer 2

if so then the only thing you can combine is the m and the -7m into a -6m. The rest of it will stay the same:
\[-(5/2)m ^{3}+(5/2)m ^{2}-6m+5\]