Answer:
C
Step-by-step explanation:
Given x and y vary directly then the equation relating them is
y = kx ← k is the constant of variation
To find k use the condition x = 20 , y = 10 then
10 = 20k ( divide both sides by 20 )
[tex]\frac{10}{20}[/tex] = [tex]\frac{1}{2}[/tex] = k
y = [tex]\frac{1}{2}[/tex] x ← equation of variation → C
