$\frac{3}{1} + \frac{3}{1+2} + \frac{3}{1+2+3} + \frac{3}{1+2+3+4} + \dots + \frac{3}{1+2+3+\dots+20} =$

$\frac{1}{7 \times 9} + \frac{1}{9 \times 11} + \dots + \frac{1}{33 \times 35} =$

$\frac{2+4}{2 \times 3 \times 4} + \frac{4+6}{4 \times 5 \times 6} + \frac{6+8}{6 \times 7 \times 8} + \dots + \frac{18+20}{18 \times 19 \times 20} =$