Question

Does y vary directly as x in this function? y = 3x

Answer 1

If it is in this form, or can be transformed into this form: y =kx,
then it is indeed a direct variation!

This is a direct variation : y = 3x
Because it's constant of variation here is 3

Answer 2

Because in order for something to be a direct variation, it can have no 'b' or y-intercept. In this problem, you can see that it follows the form of y=mx. It has no 'b' term. Therefore, it is a direct variation. 

If it were an indirect variation, i would have looked something like this...

y=3x+4...

Hope this helped!