4/3x7 + 5/7x12 + 1/12x13 + 7/13x20 + 3/20x23
=1/3-1/7+1/7-1/12+1/12-1/13+1/13-1/20+1/20-1/23
=1/3-1/23
=20/69
Kanzaki Mizuki
\(=\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}+\frac{1}{13}-\frac{1}{20}+\frac{1}{20}-\frac{1}{23}\)
\(=\frac{1}{3}-\frac{1}{23}\)
\(=\frac{20}{69}\)