Problem #$3$: Find all real numbers $x$ that satisfy the given equation.

$($a$){25}^x(\frac{1}{5}{)}^{6x}=5$

$($b$)4^{8-x}={64}^x$

$($c$)(\frac{1}{125}{)}^{30-x^2}=5^{21x}$

Problem #$3($a$)$: $$ Do not include $"x="$ in your answer.

Problem #$3($b$)$: $$

Problem #$3($c$)$: $$