Answer:
-6
Step-by-step explanation:
Undo everything being done to the variable.
7.85-2.15c=20.75
1: This is basically -2.15c+7.85 so subtract 7.85 from both sides to undo the addition.
-2.15c=12.9
2: divide both sides by -2.15 to undo the multiplication.
c=-6
