Question

Halla x en: (x+3)+(x+6)+(x+9)+...+(x+60) = 1230 ES PARA AHORA PORFISS

Answer 1

$20x + 3(\frac{20(21)}{2} ) = 1230 \\ 20x = 1230 - 630 \\ 20x = 600 \\ x = 30$