a, `2/13xx9/14+11/13xx9/14`
`=9/14xx(2/13+11/13)`
`=9/14xx13/13`
`=9/14xx1`
`=9/14`
b, `20/17+7/4-3/17-3/4`
`=(20/17-3/17)+(7/4-3/4)`
`=17/17+4/4`
`=1+1`
`=2`
`a)`
\(\dfrac{2}{13}\times\dfrac{9}{14}+\dfrac{11}{13}\times\dfrac{9}{14}\\ =\left(\dfrac{2}{13}+\dfrac{11}{13}\right)\times\dfrac{9}{14}\\ =1\times\dfrac{9}{14}\\ =\dfrac{9}{14}\)
`b)`
\(\dfrac{20}{17}+\dfrac{7}{4}-\dfrac{3}{17}-\dfrac{3}{4}\\ =\left(\dfrac{20}{17}-\dfrac{3}{17}\right)+\left(\dfrac{7}{4}-\dfrac{3}{4}\right)\\ =1+1\\ =2\)
a) \(\dfrac{2}{13}\) x \(\dfrac{9}{14}+\dfrac{11}{13}\) x \(\dfrac{9}{14}\)
\(=\dfrac{9}{14}+\left(\dfrac{2}{13}+\dfrac{11}{13}\right)\)
\(=\dfrac{9}{14}\)x\(\dfrac{13}{13}\)
\(=\dfrac{9}{14}\)x \(1\)
\(=\dfrac{9}{14}\)
b) \(\dfrac{20}{17}+\dfrac{7}{4}-\dfrac{3}{17}-\dfrac{3}{4}\)
\(=\left(\dfrac{20}{17}-\dfrac{3}{17}\right)+\left(\dfrac{7}{4}-\dfrac{3}{4}\right)\)
\(=\dfrac{17}{17}+\dfrac{4}{4}\)
\(=1+1\)
\(=2\)
