Answer:
x = 3
Explanation:
"Standard form" is the form ...
... ax + by = c
where a, b, c are mutually prime integers. The coefficients a and b cannot both be zero. The leading coefficient must be positive. If "a" is zero, then the leading coefficient is "b".
So ...
... x = 3
is in standard form already. (a=1, b=0, c=3)
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Further comments on Standard Form
Of course, if the line has irrational slope or intercept, the coefficients cannot all be integers.
The order of the variables may be swapped, in which case the coefficient of y is the leading coefficient and must be positive.
This is the only way a vertical line can be written, as slope-intercept form is undefined for a vertical line.