Answer
4.5
Work Step by Step
At the half point: pH=pKa
Line A is the weak acid (because it has a higher pH)
To find the half point:
Find the midpoint of the slope before the slope sharply escalates. For line A, that slope falls between about 3 to 6 on the y axis and between about 0 to before 30 on the x axis. The middle of that slope lands by about 4.5 on the y axis
So pH= 4.5
and at the half point pH=pKa=4.5
