Answer
Subtraction is not associative.
Refer to the step-by-step part below for the explanation.
Work Step by Step
Subtraction will be associaitive if for all real numbers $a, b, $ and $c$,
$(a-b)-c = a-(b-c)$
However, note that:
$(1-2)-3=-1-3=-4$
while
$1-(2-3)=1-(-1) = 1+1=2$
Thus, $(a-b)-c \ne a-(b-c)$.
Therefore, subtraction is NOT associative.
