y varies directly as x, and y=20 when x=5

y = 4x

When two variables vary directly, it means that they are related by a constant ratio. In this case, we can say that y varies directly as x. Mathematically, this can be represented as:

y = kx

where k is the constant of variation.

To find the value of k, we can use the given information that y = 20 when x = 5. Substituting these values into the equation, we get:

20 = k(5)

Now we can solve for k by dividing both sides of the equation by 5:

k = 20/5 = 4

So the constant of variation in this case is 4. Therefore, the equation that represents the direct variation between x and y is:

y = 4x