Stuck on an Angular Motion question.

Basketball is spinning on top a finger. The angular velocity of the ball slows down from 18.5 to 14.1 rad/sec. During this time, the angular displacement is 85.1 rad. Determine the time it takes for this to happen.

So theta is 85.1 rad,

for the 18.5 and 14.1 do I subtract the two? to get omega?

I am not sure and going thru my notes I can't find what I am looking for, so not sure what to do?

Which formula do I use as well. wouldn't be w=theta/time?

If someone can get me started would be great, thanks for looking.