Can someone help me this please

Answer:
5
Step-by-step explanation:
[tex]23=-6(-3)+c\\[/tex] Plug in the given x- and y-coordinates (in this case we'll use [tex]c[/tex] for the missing variable)
[tex]23=18+c[/tex] Simplify
[tex]5=c[/tex] Subtract 18 from both sides (Subtraction Property of Equality)