If the speed of an object from 121m's to 98m's during a time interval of 12s what is the accelerations of the object?

Average acceleration is a net change in velocity over a corresponding change in time.

Your velocity went from 65 to 98 m/s - that's a positive change (gain) of 33 m/s.
the time interval was 12 s.

+ 33/12 m/s/s = + 2.75 m/s/s.