Question

Answer 1

a \(\dfrac{2}{5}+\dfrac{3}{8}+\dfrac{7}{20}=\dfrac{16}{40}+\dfrac{15}{40}+\dfrac{14}{40}=\dfrac{9}{8}\)

b \(\dfrac{5}{9}+\dfrac{7}{12}-\dfrac{3}{4}=\dfrac{20}{36}+\dfrac{21}{36}-\dfrac{27}{36}=\dfrac{7}{18}\)

Answer 2

Lời giải:

a.

$\frac{2}{5}+\frac{3}{8}+\frac{7}{20}=\frac{16}{40}+\frac{15}{40}+\frac{14}{40}$

$=\frac{45}{40}=\frac{9}{8}$

b.

$\frac{5}{9}+\frac{7}{12}-\frac{3}{4}=\frac{20}{36}+\frac{21}{36}-\frac{27}{36}=\frac{14}{36}=\frac{7}{18}$

 

Answer 3

`2/5 + 3/8 + 7/20= 31/40 + 7/20= 9/8`

`5/9 + 7/12 - 3/4= 41/36 - 3/4= 41/36 - 27/36=14/36= 7/18`