Applying PEMDAS
P ----> Parentheses first
E -----> Exponents (Powers and Square Roots, etc.)
MD ----> Multiplication and Division (left-to-right)
AS ----> Addition and Subtraction (left-to-right)
Parentheses first
[tex]\begin{gathered} (2-4)=-2 \\ (6-3)=3 \\ \end{gathered}[/tex]substitute
[tex]\begin{gathered} (-2)2-5(3)+13 \\ -4-15+13 \\ -4-2 \\ -6 \\ \end{gathered}[/tex]The student error was misapplication of the comutative property