I need help on this please.

Question

Find the partial sum  for the arithmetic sequence with 

S12=________

Answer 1

There's a formula for the sum of the first n terms of an arithmetic sequence. You should look it up in your textbook (or other learning material). It's

S_n = (n/2)*(a₁+a_n)

Use the definition of an arithmetic sequence to find a_n = a₁ + (n-1)*d