THE 28TH TERM OF AN AP IS -5 FIND ITS COMMON DIFFERENCE IF ITS TERM IS 31

Answer 1

You say "its term is 31"
Does that mean its 1st term? If so, then
a28 = a+27d, so
31+27d = -5

If not, remember:
It's not my job to figure out what you mean.
It's your job to say it so clearly you cannot be misunderstood.