So, in order to find an equation of a line, first we need to find the slope.
To find the slope, we will use the following equation

So, when we plug our numbers in we get

So, we now know our slope is 7. Now we can use slope-intercept since the Y-intercept is already given (0,0)
Slope intercept form has the following general formula

M is the slope, and b is the Y-intercept.
So, we get

Y=7x is the equation