3.) Point slope form => y - y1 = m(x - x1); where (x1, y1) ia a point which is on the line and m is the slope.
Line x + 2y = 3 => 2y = 3 - x => y = -1/2x + 3/2 => slope is -1/2
a.) For parallel lines m1 = m2 (i.e. slopes are equal)
Required equation: y - 0 = -1/2(x - 2)
b.) For perpendicular lines, m2 = -1/m1 = -1/(-1/2) = 2
Required equation: y - 0 = 2(x - 2)