Answer:
See below
Explanation:
m = slope of line graph
=

For each line, select two points whose x- and y-coordinates will be substituted in the above formula to calculate the slope
For line a:
I chose points
=

and
=

∴
=

=

∴m = 1
For line b:
I chose points
=

and
=

∴
=

=

∴m =
or

For line c:
I chose points
=

and
=

∴
=

=

=

∴ m = 1