Answer
$x = \frac{1}{2}$
Work Step by Step
RECALL:
(1) $a^m \cdot a^n = a^{m+n}$
(2) If $a^m=a^n$, then $m=n$
Use rule (1) above to obtain:
$5^{2x+4x}=125
\\5^{6x}=125$
Note that $125=5^3$.
Write $125$ as $5^3$ to obtain:
$5^{6x} = 5^3$
Use rule (2) above to obtain:
$6x=3$
Divide $6$ on both sides of the equation to obtain:
$x = \frac{1}{2}$
