Suppose that y varies directly with x, and y= 8 when x= 16.

Answer 1

If "y" varies directly with "x", that means y = kx where "k" is called the constant of proportionality. To find "k", use the information that y = 8 when x = 16:

8 = k(16) now divide both sides by 16 to get k = 1/2

That means the equation that models this situation is y = (1/2)x

You do not specify what you would like to do with this information but you can find the value of "y" for any given "x" with this, or visa versa.