Chapter R - Section R.4 - Properties of Real Numbers - R.4 Exercises - Page 38: 39

$-6z-39$

Using $a(b+c)=ab+ac$ or the Distributive Property and then combining like terms, the given expression, $ 2+3(2z-5)-3(4z+6)-8 ,$ simplifies to \begin{array}{l}\require{cancel} 2+6z-15-12z-18-8 \\\\= (6z-12z)+(2-15-18-8) \\\\= -6z-39 .\end{array}