Answer:
see explanation
Step-by-step explanation:
Given that y is inversely proportional to x then the equation relating them is
y = [tex]\frac{k}{x}[/tex] ← k is the constant of proportion
(a)
To find k use the condition when y = 7 , x = 9, that is
7 = [tex]\frac{k}{9}[/tex] ( multiply both sides by 9 )
63 = k
y = [tex]\frac{63}{x}[/tex] ← equation of proportion
(b)
When x = 21, then
y = [tex]\frac{63}{21}[/tex] = 3
