a: \(\dfrac{7}{8}+3=\dfrac{3\cdot8+7}{8}=\dfrac{31}{8}\)
b: \(2-\dfrac{5}{4}=\dfrac{2\cdot4-5}{4}=\dfrac{3}{4}\)
\(4\cdot\dfrac{5}{9}=\dfrac{20}{9}\)
d: \(\dfrac{3}{8}:2=\dfrac{3}{16}\)
Câu a: 7/8 + 3= 7/8 + 24/8= 31/8
Câu b: 2-5/4= 8/4 - 5/4= 3/4
Câu c: 4 x 5/9= 20/9
Câu d: 3/8 : 2= 3/16