a: =1/5+4/5+4/11+7/11
=1+1
=2
b: =5/6+5/9-1/4
=30/36+20/36-9/36
=41/36
\(\dfrac{1}{5}+\dfrac{4}{11}+\dfrac{4}{5}+\dfrac{7}{11}=\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\left(\dfrac{4}{11}+\dfrac{7}{11}\right)=\dfrac{5}{5}+\dfrac{11}{11}=1+1=2\)
\(\dfrac{5}{6}+\left(\dfrac{5}{9}-\dfrac{1}{4}\right)=\dfrac{5}{6}+\left(\dfrac{20}{36}-\dfrac{9}{36}\right)=\dfrac{5}{6}+\dfrac{11}{36}=\dfrac{30}{36}+\dfrac{11}{36}=\dfrac{41}{36}\)
`1/5+4/5+4/11+7/11=(1/5+4/5)+(4/11+7/11)=1+1=2`
`5/6+5/9-1/4=30/36+20/36-9/36=41/36`
