Posted by Anonymous on Wednesday, October 12, 2011 at 5:06am.
13th term is 27 --- a + 12d = 27
the 7th iterm is 3 times the 2nd term --> a+6d = 3(a+d)
or
a+6d = 3a + 3d
2a = 3d
a = 3d/2
sub into the first equation
3d/2 + 12d = 27
3d+24d=54
d = 2
then a = 3(2)/2 = 3
I will let you finish it for the sum, you did not say how many terms you want to add.
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