SEAMO X 2019 — Paper C — Lớp 5–6 Câu hỏi 12

Cho $1-\dfrac1{r+\dfrac1{s+\dfrac1{t+\dfrac1{u+1/s}}}}=\dfrac1{1+\dfrac1{2+\dfrac1{2+\dfrac1{3+1/3}}}}$, tìm $r+s+t+u$.