Answer
$For\,\,all\,\,sets\,\,A,\,B,\,and\,\,C\,\\
A - (B - C) = (A - B) - C \\
this\,\,is\,\,false\\
counter\,\,example\,\,:\\
A=\left \{ 1,2,3,4 \right \},B=\left \{ 2,3 \right \},C=\left \{ 3,4 \right \}\\
$
Work Step by Step
$For\,\,all\,\,sets\,\,A,\,B,\,and\,\,C\,\\
A - (B - C) = (A - B) - C \\
this\,\,is\,\,not\,\,true:\\
counter\,\,example\,\,:\\
A=\left \{ 1,2,3,4 \right \},B=\left \{ 2,3 \right \},C=\left \{ 3,4 \right \}\\
B-C=\left \{ 2 \right \}\\
A - (B - C)=\left \{ 1,2,3,4 \right \}-\left \{ 2 \right \}=\left \{ 1,3,4 \right \}\,\,\,\,\,(1)\\
A-B=\left \{ 1,4 \right \}\\
(A - B) - C=\left \{ 1 \right \}\,\,\,\,\,(2)\\
from\,\,1,2\,\,:\\
A - (B - C) =\left \{ 1,3,4 \right \}\neq \left \{ 1 \right \}= (A - B) - C \\
$
