Official solution
\[\because\] Given statement is
(A \[\wedge\] C) \[\to\] B
Then its negation is
\[\sim\] {(A \[\wedge\] C) \[\to\] B}
or \[\sim\] {\[\sim\] (A \[\wedge\] C) \[\vee\] B}
\[\therefore\] (A \[\wedge\] C) \[\wedge\] (\[\sim\] B)
or (\[\sim\] B) \[\wedge\] (A \[\wedge\] C)