First, we can simplify the equation by rewriting 64 as 4^3:

4^5x - 10 = 4^3

Now, we can rewrite both sides of the equation with the same base:

2^(2*5x) - 10 = 2^(3)

Using the properties of exponents:

2^(10x) - 10 = 8

Now, substitute 8 as 2^3:

2^(10x) - 10 = 2^3

Now the bases are the same, so we can set the exponents equal to each other:

10x = 3

Divide by 10 on both sides:

x = 3/10

So, x = 0.3

Combine the two terms on the left side:

3^(2x - 4) = 21

Rewrite 21 as 3^3:

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

Now, the bases are the same, so we can set the exponents equal to each other:

2x - 4 = 3

Add 4 to both sides:

2x = 7

Divide by 2 on both sides:

x = 7/2

So, x = 3.5