Answer:
see explanation
Step-by-step explanation:
since y is inversely proportional to x the equation relating them is
y = [tex]\frac{k}{x}[/tex] ← k is the constant of proportionality
to find k use the given condition when y = 7, x = 9
k = yx = 7 × 9 = 63
y = [tex]\frac{63}{x}[/tex] ← is the equation connecting them
when x = 21, then
y = [tex]\frac{63}{21}[/tex] = 3
