Intermediate Algebra: Connecting Concepts through Application

$-4x+16$
The student did not change the sign of $-9$ when the parentheses were removed. The correct simplified expression of $(2x+7)-(6x-9) ,$ is \begin{array}{l}\require{cancel} 2x+7-6x+9 \\\\= 2x+7-6x+9 \\\\= (2x-6x)+(7+9) \\\\= -4x+16 .\end{array}