Since its a straight line graph just make an equation in the form y=mx+c.
That will turn into y=1/3x+c
But we need to solve for the y intercept (c)
Just substitute in the point u have (3,6)
6=1/3(3)+c
6=1+c
C is 5
So the equation is y=1/3x+5
On your graph plot the y intercept (5) and the coordinate (3,6)
Then draw a line crossing the intercept and the co-ordinate (3,6)
I hope this helps!
