Question 939114
#9 only:


x for how many months of cleanup
y for how much remains


Identify ordered pairs:
(3,880), and then time 3+2 months or 5 months, 800 cubic yards, so (5,800).


Form the equation of the line in slope-intercept form:
{{{m=(800-880)/(5-3)=-80/2=-40}}};
-
{{{y=mx+b}}}
{{{b=y-mx}}}
b=pick a point,
{{{b=800-(-40)5}}}
{{{b=800+200}}}
{{{b=1000}}}
-
{{{highlight(y=-40x+1000)}}}


The analysis of and solution to #9 should help with the previous two questions.