Please solve using coq

Require Import ZArith.

$(**$

Instructions

$-$ Replace $[$Abort$.]$ with $[$Qed$.]$ after you successfully solve a problem.

$-$ If you can't solve a problem, comment out your code $($if any$)$ and

end the problem with $[$Abort$.]$ instead of $[$Qed$.]$ In Coq, the

syntax for comment is $[(*$ comment goes here $*)].$

$-$ The number of submissions is unlimited.

$-$ Deadline: Apr $25$ @ $23$:$55$

$*)$

Open Scope Z$\_$scope.

Theorem mod$\_$mult$\_$or :

forall a b c : Z$,($a $|$ b$)\backslash /($a $|$ c$)->($a $|$ b $*$ c$).$

Proof.

Abort.

Theorem mod$\_$mult :

forall a b c : Z$,($a $|$ b$)/\backslash ($a $|$ c$)->($a $|$ b $*$ c$).$

Proof.

Abort.

Close Scope Z$\_$scope.