Chapter 5 - Exponents and Polynomials - 5.2 - Multiplying Monomials - Problem Set 5.2 - Page 201: 63

$-2x-9y$

Using $a(b+c)=ab+ac$, or the Distributive Property, and then combining like terms, the given expression, $ 4(x-3y)-3(2x-y) ,$ simplifies to \begin{array}{l}\require{cancel} 4x-12y-6x+3y \\\\= (4x-6x)+(-12y+3y) \\\\= -2x-9y .\end{array}