Which of the following is a linear function?

one over three x = y − 3
y = x3 + 2
y = 6x2
y = two over three x

There are two possible linear functions. The first one is 1/3x = y - 3. The second one is y = 2/3x.

I figured this out by plugging in the four equations into a graphing calculator. If you don't have one, I recommend using an online graphing calculator. I know that a linear function is a straight line on a graph. 

If you look at the graph I have attached, you can see that there is only two straight lines. From this, you can find out which expression is a linear function.

I hope this helps!

Dwould be the answer