Chapter 5 - Section 5.4 - Polynomials in Several Variables - Exercise Set - Page 375: 9

$7x^2y-4xy$

Removing the grouping symbols and then combining like terms, the given expression, $ (5x^2y-3xy)+(2x^2y-xy) ,$ simplifies to \begin{array}{l}\require{cancel} 5x^2y-3xy+2x^2y-xy \\\\= (5x^2y+2x^2y)+(-3xy-xy) \\\\= 7x^2y-4xy .\end{array}