a)
[tex]\it x=\Big(\dfrac{5}{\sqrt8}-\dfrac{7}{\sqrt2}\Big)\cdot\dfrac{\sqrt2}{6}=\dfrac{5}{12}-\dfrac{^{2)}7}{\ \ 6}=\dfrac{5-14}{12}=-\dfrac{\ 9^{(3}}{12}=-\dfrac{3}{4}[/tex]
b)
[tex]\it y=(\dfrac{1}{\sqrt5}+\dfrac{3}{\sqrt{80}})\cdot\sqrt5=1+\dfrac{3}{4}\\ \\ \\ x+y=-\dfrac{3}{4}+1+\dfrac{3}{4}=1\in\mathbb{N}[/tex]
