Solve for S_13
S_{13}=416
Assign S_13
S_{13}≔416
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S_{13}=\frac{13\times 64}{2}
Subtract 10 from 74 to get 64.
S_{13}=\frac{832}{2}
Multiply 13 and 64 to get 832.
S_{13}=416
Divide 832 by 2 to get 416.
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