Answer:
[tex]\large\boxed{3.\ \dfrac{1}{625t^{12}}}[/tex]
Step-by-step explanation:
[tex]\text{Use}\\\\(ab)^n=a^nb^n\\\\(a^n)^m=a^{nm}\\\\a^{-n}=\dfrac{1}{a^n}\\---------------\\\\(5t^3)^{-4}=\dfrac{1}{(5t^3)^4}=\dfrac{1}{5^4(t^3)^4}=\dfrac{1}{625t^{(3)(4)}}=\dfrac{1}{625t^{12}}[/tex]
