Well, I can see where you got both the numerator and denominator but those are for t= 15 and 20 and don't give any information about t= 22.Then I did (4.5-7)/(20-15) and got -.5.
I must confess that why you are doing makes no sense. Why would you add those results and divide by 2?I added -.42 and -.5 and got -.92 and divided that by 2 and my answer was: -.46 which makes no sense..?
The time given, t= 22, is not on the table but lies between t= 20 and t= 25. The average rate of change of v between those is