Answer :

[tex]c-(-17.6)=-4 \\\\ c+17.6=-4 \\\\ c=-4-17.6 \\\\ \boxed{c=-21.6\to \ variant \ A}[/tex]
[tex]c-(-17.6)=-4\\\\c+17.6=-4\ \ \ \ |subtract\ 17.6\ from\ both\ sides\\\\c=-21.6\\\\Answer:\boxed{A}[/tex]