# The variables x=9 and y=15 varies directly. How do you write an equation that relates the variables and find x when y=-5?

The equation is

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To write an equation that relates the variables x and y when they vary directly, you use the formula:

y = kx

where k is the constant of variation.

Given that x = 9 and y = 15 when they vary directly, we can find k:

15 = k * 9 k = 15/9 = 5/3

Now, we can write the equation relating x and y:

y = (5/3)x

To find x when y = -5, we substitute y = -5 into the equation and solve for x:

-5 = (5/3)x x = -5 * (3/5) x = -3

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