4^(2x - 5) = 64

=> 4^(2x - 5) = 4^3

as 4 is equal we equate the exponent

2x - 5 = 3

=> 2x = 3 + 5

=> x = 8/2

=> x = 4

Now we have the 6 terms of which 4 is one term, so the probability of picking 4 when any number from the set is picked is 1/6.

**The required probability is 1/6**