Question 8606
You begin by calculating the slope of the line through those points.
{{{(30-0)/(3-0)=10}}}
So the line has the slope-intercept form 
{{{y = 10x + b}}}
We know y = 0 when x = 0, so the y-intercept is 0.
The equation is
{{{y = 10x + 0}}} or just {{{ y = 10x}}}