For this to work i did draw diagrams and i came up with example of functions.
Let F be the sets of all functions from the set of integers to set of integers. Prove or disapprove:
FALSE
$\forall f,g,h \in F$ if $ f\circ h = g \circ h$ then $f=g$
Now, i prove the negation is true. Let $f,g,h$ be the functions from set of integers to set of integers defined as
$f=\{(3,1),(4,2),(5,2)\}$
$g=\{(3,2),(4,2),(5,2)\}$
$h=\{(1,3),(2,5)\}$
$ f\circ h = \{(1,1),(2,2)\}$
$g \circ h = \{(1,1),(2,2)\}$
We see that $ f\circ h = g \circ h$ . Also, $f\not= g$ because $\{(3,1),(4,2),(5,2)\} \not= \{(3,2),(4,2),(5,1)\} $ .
In other words, for input in function $f$ there is an output that has to be equal for function $g$ if the input given is that of $f$.
$f=\{(0,7),(1,4)\}$
$g=\{(0,7),(1,5)\}$
$h \equiv 0$ disproves.