Because [tex]x[/tex] and [tex]y[/tex] are inversely proportional, there is some constant [tex]k[/tex] such that
[tex]xy=k[/tex]
Given that [tex]y=42[/tex] and [tex]x=6[/tex], we have
[tex]k=6\times42=252[/tex]
So when [tex]x=9[/tex], you have
[tex]9y=252\implies y=\dfrac{252}9=28[/tex]
