In the general form, the standard form looks like this:

First, get the equation of the line in a slope-intercept form then change it into a standard form equation.
The slope-intercept form looks like this in general form:

Find two points on the plain and use the slope formula. In the picture above, they have already marked two points on the line.

Now get the y-intercept form. By looking at the graph, the line intercepts at the point (0, 1/2).
Plug these into the slope-intercept form.
y = (1/2)x + (1/2)
Convert the slope-intercept form into a standard form.
y = (1/2)x + (1/2)
2y = x + 1 <-- Multiplied each side by 2
2y - x = 1 <-- Subtracted each side by x
The third option is the correct answer because 2y - x = 1 can be rearranged to become -x + 2y = 1.