Đáp án+Giải thích các bước giải:
$\\B=1,25.\dfrac{7}{19}+\dfrac{5}{4}.\dfrac{15}{19}-\dfrac{\dfrac{1}{1}}{4}.\dfrac{3}{19}\\=\dfrac{5}{4}.\dfrac{7}{19}+\dfrac{5}{4}.\dfrac{15}{19}-\dfrac{\dfrac{1}{1}}{4}.\dfrac{3}{19}\\=\dfrac{5}{4}.\left(\dfrac{7}{19}+\dfrac{15}{19}\right)-\dfrac{3}{76}\\=\dfrac{5}{4}.\dfrac{22}{19}-\dfrac{3}{76}\\=\dfrac{55}{38}-\dfrac{3}{76}\\=\dfrac{107}{76}$