Answer: a. 21 terms
b. 798
Step-by-step explanation:
a. 68-8=60 ==> difference between 1st and last term
60/3=20 ==> number of terms after the first term
20+1=21 terms ==> total number of terms
b. Find the mean of the terms first:
(68+8)/2= ==> the mean of all terms in a sequence is equal to the mean of the first and last term
76/2=38
38*21=798 ==> add the mean 21 times to get the total sum since there are 21 terms in the sequence.
