Answer:
y = 42
Step-by-step explanation:
given y varies as x then
y = kx ← k is the constant of variation
to find k use the given condition y = 21 when x = 8
k = [tex]\frac{y}{x}[/tex] = [tex]\frac{21}{8}[/tex], hence
y = [tex]\frac{21x}{8}[/tex]
when x = 8 then y = [tex]\frac{21(16)}{8}[/tex] = 42
