Xin lỗi các bạn : B = 53/117 *129/311+53/117*43/311--64/117*172/311
đề bài này mới đúng nhé mong các bạn bỏ qua.Thank
\(B=\frac{53}{117}\times\frac{129}{311}+\frac{53}{117}\times\frac{43}{311}-\frac{64}{117}\times\frac{172}{311}\)
\(=\frac{53\times129}{117\times311}+\frac{53\times43}{117\times311}-\frac{64\times172}{117\times311}\)
\(=\frac{53\times43\times3+53\times43+64\times4\times43}{117\times311}\)
\(=\frac{43\times\left(53\times3+53+64\times4\right)}{117\times311}\)
\(=\frac{43\times\left[53\times\left(3+1\right)+64\times4\right]}{117\times311}\)
\(=\frac{43\times\left[53\times4+64\times4\right]}{117\times311}\)
\(=\frac{43\times4\times\left(53+64\right)}{117\times311}\)
\(=\frac{172\times117}{117\times311}=\frac{172}{311}\)