Since AC = BC, we can say that this triangle is isoceles (at C)
In an isoceles triangle, the two angles that does not belong to the top angle (which in this case is C) is equal to each other.
Now, we can find the sum of the 2 missing angles : 180 - 52 = 128.
And since they are equal, we can find b : 128 : 2 = 64/