Rút gọn \(A = \frac{{\frac{1}{2} + \frac{1}{3} + \...

Câu hỏi: Rút gọn \(A = \frac{{\frac{1}{2} + \frac{1}{3} + \frac{1}{4} + ... + \frac{1}{{19}} + \frac{1}{{20}}}}{{\frac{{19}}{1} + \frac{{18}}{2} + ... + \frac{2}{{18}} + \frac{1}{{19}}}}\)

A. 20

B. 30

C. -20

D. -30