Question

thuận tiện : 
\(2\dfrac{13}{21} x \dfrac7{15} + 2\dfrac{13}{21} x \dfrac8{15}\)

Answer 1

` 2 13/ 21 xx 7/15 + 2 13/21 xx 8/15`

`=2 13/21 xx(7/15 + 8/15)`

`=55/21 xx 1=55/21`

Answer 2

\(=\dfrac{55}{21}\cdot\dfrac{7}{15}+\dfrac{55}{21}\cdot\dfrac{8}{15}=\dfrac{55}{21}\cdot\left(\dfrac{7}{15}+\dfrac{8}{15}\right)=\dfrac{55}{21}\cdot1=\dfrac{55}{21}\)