I understand the basics of variations, but am having trouble when numbers are applied. For example, I have the following problem:

"Assume that

*y* is directly proportional to

*x*. Use the given

*x*-value and

*y*-value to find a linear model that relates

*y* and

*x*.

*x* =

9,

*y* =

36 "

y is directly proportional to x ... y = kx

**y = 4x** ... would be a linear equation, right?

The same goes for this problem:

"Find a mathematical model representing the statement. (In each case, determine the constant of proportionality.)

*y* is inversely proportional to

*x*. (

*y* = 7 when

*x* =

32.)"

y is inversely proportional to x ...