You write it as a improper fraction first*
20
-----
8
and then u divide 8 into 20
and we know that it goes in it 2.5 times
so simply from here
it is 2.5%
point slope form:y-2=4(x+1)
then distribute 4 and simplify y-2=4x+4 , y=4x+6 is the slope -y intercept form
then, move 4x on the left side, you get -4x+y=6 , multiply every term by -1, you get 4x-y=-6 which is standard form.
If they sold 89 calendars over 4 weeks, the 'equation' would look like (x = average calendars sold over 4 weeks):

If you solve it, you get:

Which is equal to
22.25. Hope this helps!