The value of y varies directly with x. If x = 15, then y = 12. What is the value of y, when x = 21?

y = 16.8

Step-by-step explanation:

Given that y varies directly with x then the equation relating them is

y = kx ← k is the constant of variation

To find k use the condition x = 15 when y = 12, that is

12 = 15k ( divide both sides by 15 )

= k, so

k = 0.8 y = 0.8x ← equation of variation

When x = 21, then

y = 0.8 × 21 = 16.8

$15 each

step-by-step explanation:

$45/3 children= $15 each