To evaluate an expression we have to plugg in the value that is given. Think of the first one
[tex]-3x+4x+5[/tex]Since the value of x is -2, we substitute the value in the expression
[tex]\begin{gathered} -3(-2)+4(-2)+5=6-8+5 \\ =3 \end{gathered}[/tex]So the first expression has a value of 3 when x=-2.
For the second one we have the expression
[tex]6-(5x-9)[/tex]For x=1, we have
[tex]\begin{gathered} 6-(5(1)-9)=6-(5-9) \\ =6-(-4) \\ =6+4 \\ =10 \end{gathered}[/tex]So the second expression has a value of 10 when x=1.
For the last one we have
[tex]n-1-m-n[/tex]where m=-2 and n=3. Then
[tex]\begin{gathered} 3-1-(-2)-3=3-1+2-3 \\ =1 \end{gathered}[/tex]So the last expression has the value of 1 when m=-2 and n=3.
