Chapter 1 - Introduction to Algebraic Expressions - 1.8 Exponential Notation and Order of Operations - 1.8 Exercise Set - Page 67: 78

$\dfrac{5}{4}$

Substituting $ t $ with $ -6 $ in the given expression, $ -30\div t(t+4)^2 $, then, \begin{array}{l}\require{cancel} -30\div (-6)(-6+4)^2 \\\\= -30\div (-6)(-2)^2 \\\\= -30\div (-6)(4) \\\\= -30\div (-24) \\\\= \dfrac{\cancel{-6}\cdot5}{\cancel{-6}\cdot4} \\\\= \dfrac{5}{4} .\end{array}