Answers

2016-06-30T08:44:47+08:00
D= 54-60 = 6
A1=12

a8= a1+(n-1)d
54=a1+(8-1)6
54=a1+(7)6
54=a1+42
54-42=a1
12=a1
2 4 2
2016-06-30T19:50:26+08:00
To find the common difference minus the 2nd term to the first term
                   60-54=6            6 in the common difference

an=a1+(n-1)d
a8=a1+(8-1)(6)
54=a1+(7)(6)
54=42a1          trans post the 42 
54-42=a1
12=a1
1 1 1