Explanation:
this is a college question ???
and you don't know how to do this ?
remember middle school and high school ? besides math classes themselves, did you never track your class scores and such ?
the average or mean value is always the sum of all data points divided by the number of data points.
here we have 6 data points.
the average is
(20+25+7+27+18+17)/6 = 114/6 = 19