Question

find the 12the term from the end of the following ap 3,5,7,9....201

Answer 1

Hi Jake !
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AP = 3,5,7,9,...,201 
a1 = 3 
a2 = 5 
a3 = 7 
d = a2-a1 
   =  5-3 
   =  2 
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Then, a12 = a1+(n-1)d
                  = 3  +(11)2
                  = 3  +22
                  =  25 
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Answer 2

this is the answer of your question, and,
the common difference went negative because we are assuming the last term to be the first term.