Solution:
In an isosceles triangle, the base angles are congruent, which means that each base angle is equal to the third angle divided by 2.

Therefore, to find the third angle, we can multiply each given base angle by 2.

(a) The third angle would be 2 * 64 = 128 degrees.
(b) The third angle would be 2 * 42 = 84 degrees.
(c) The third angle would be 2 * 18 = 36 degrees.
(d) The third angle would be 2 * 82 = 164 degrees.