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 proportionality
To find k use the condition that y = 7, x = 9
k = yx = 7 × 9 = 63, thus
y = [tex]\frac{63}{x}[/tex] ← equation of proportion
When x = 21, then
y = [tex]\frac{63}{21}[/tex] = 3
