Đáp án đúng: B
Giải chi tiết:\(\begin{array}{l}\frac{{1313}}{{1212}}:x = \frac{1}{{1 \times 2}} + \frac{1}{{2 \times 3}} + \frac{1}{{3 \times 4}} + \frac{1}{{4 \times 5}} + \frac{1}{{5 \times 6}}\\\,\,\,\,\,\frac{{13}}{{12}}:x = 1 - \frac{1}{6}\\\,\,\,\,\,\frac{{13}}{{12}}:x = \frac{5}{6}\\\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{{13}}{{12}}:\frac{5}{6}\\\,\,\,\,\,\,\,\,\,\,\,\,\,x = \frac{{13}}{{10}}\end{array}\)
Đáp số: \(x = \frac{{13}}{{10}}\).
Chọn B.