Answer:
y = 24
Explanation:
Given y is directly proportional to
then the equation relating them is
y = k
← k is the constant of proportion
To find k use the condition when x = 28, y = 20 , then
20 = k ×
= k ×
= 5k ( divide both sides by 5 )
4 = k
y = 4
← equation of proportion
When x = 39 , then
y = 4 ×
= 4 ×
= 4 × 6 = 24