What is the equation of the horizontal line through (-4, 6)?

The equation of a horizontal line is
y
=
c
for some constant
c
Since we are told that the line passes through
(
x
,
y
)
=
(
−
4
,
6
)
Then for at least one point on the line
y
=
6
But for a horizontal line this value is a constant for all points on the line.
So the equation for all points on the line is
y
=
6

Let the sales amount be x.

8% of x = 2560

0.08x = 2560

The equation is 0.08x = 2560.