$ S_20 = \frac202 (2 \times 5 + 19 \times 3) = 10 (10 + 57) = 10 \times 67 = 670 $. - AMAZONAWS

📅 March 6, 2026 👤 scraface

Mar 06, 2026

$$ S_{20} = \frac{20}{2} (2 \times 5 + 19 \times 3) = 10 (10 + 57) = 10 \times 67 = 670 $.$