Question 1133923
the midpoint is the middle of the x values and of the y values, which is (1, 1)
The perpendicular bisector has slope which is the negative reciprocal of the slope of AB, and the latter slope is (2/-4) or -(1/2).  
Point slope formula y-y1=m(x-x1), m slope and (x1, y1) a point.  For the equation of AB, it is y-0=(-1/2)(x-3) or y=(-1/2)x+(3/2)

For the perpendicular line, the slope is 2  and the point slope equation is y-1=2(x-1) or y=2x-1.  That reaches the x-axis at y=0 so 2x-1=0 and x=0.5, so the point is (0.5, 0)

reaches x-axis where y=0 or 2x=6 and x=3, so (3, 0) is point
Distance to A (PA) is sqrt (difference in x^2+difference in y^2) or sqrt (1.5^2+2^2)=sqrt(6.25) or 2.5 units.  Of course, the distance between (0.5, 0) and (3, 0) is 2.5 units ANSWER

{{{graph(300,300,-1,3,-2,2,2x-1,(-1/2)x+(3/2))}}}