8th grade math homework

Question

if y varies directly with x and y = -38 when x = 19, find x when y = -4

Answer 1

first you want to find the constant of proportionality (k) by taking

k = y/x = -38/19 = -2

meaning that the equation to solve for this situation is

y = kx

-4 = -2x

x = -4/-2 = 2

so the value of x is 2 when y = -4

Answer 2

Use the formula, y=kx. Where k is a constant we have to solve first.

We are first given y = -38 when x = 19. Enter the values into the equation.

-38 = k(19)

Divide both sides by 19.

-38/19 = k

So, k = -2.

Solve for x now when y = -4.

y= kx

-4 = -2x

-4 / -2 = x

x = 2