Mean
add up numbers and divide by how many there are
(1+1+5+3+6+6)/7=3 and 2/3
If you mean how do you get x by it's you divide both sides by 8, to cancel out the multiplication between x and 8, meaning that it would end up being x=7, sorry if that didn't answer your question correctly.
The slope-intercept form of a line is
y=mx+b
where m is the slope
b is the y-intercept
if you convert the function into an equation, then
y=4-5x
rearranging the equation
y=-5x +4
thus
m=-5 and b=4
the y-intercept of the function is 4
We find the value for s here.
8s = 1/2

1/2 divided by 8/1 = 1/2 * 1/8 = 1/16
s = 1/16