Substitute the values of a nad b to the expression:
[tex]125a^0b^4=(125)\left(\dfrac{5}{7}\right)^0\left(-\dfrac{1}{5}\right)^4=(125)(1)\left(\dfrac{1^4}{5^4}\right)\\\\=(125)\left(\dfrac{1}{625}\right)=\dfrac{125}{625}=\dfrac{125:125}{625:125}=\dfrac{1}{5}[/tex]
