The equation of any line parallel to x + y = 3
will be of the form: x + y = ??
To find ?? replace the point (10, 10) into the equation: x + y = ??
10 + 10 = 20 = ??
So, the equation will be: x + y = 20
To place this into slope-intercept form: x + y = 20
y = -x + 20