"use a system of linear equations to solve each problem"?

i hate word problems and i DO NOT understand them!
please help me (or tell me how to do them) with these 2 problems!


1) Suppose you are starting an office-cleaning service. you have spent $315 on equipment. To clean an office, you use $4 worth of supplies. You charge $25 per office. How many must you clean to break even?



2) On a canoe trip, Rita paddled upstream (against the current) at an average speed of 2 mi/h relative to the riverbank. On the return trip downstream (with the current), her average speed was 3 mi/h. Find Rita's paddling speed in still water and the speed of the river's current.





please help me!
if you do, THANK YOU SO MUCH! :]

I LOVE work problems so I hope I can help you.

1) Suppose you are starting an office-cleaning service. you have spent $315 on equipment. To clean an office, you use $4 worth of supplies. You charge $25 per office. How many must you clean to break even?

let x= # of offices you clean
you get 25/office, but spend 4, so you net 21

21x=315
x=15

if you clean 15 offices you break even
--------------------------------------...

2) On a canoe trip, Rita paddled upstream (against the current) at an average speed of 2 mi/h relative to the riverbank. On the return trip downstream (with the current), her average speed was 3 mi/h. Find Rita's paddling speed in still water and the speed of the river's current.
x=her rate,
y=current's rate

x+y=rate with current=3
x-y=rate against current=2

x+y=3
x-y=2

add

2x=5

x=2.5mph
y=.5mph

1) To break even, have to make $315. Let x be the number of offices to clean, then
(25-4)x = 315 where 4 represents the cost/office
x = 315/21 = 15

2) Let x be the speed of the river's current
Let s be her speed in still water, then
x - s = 2
x + s = 3
2x = 5
x = 5/2
s = 3- 5/2 = 1/2

1)
The answer is: (x is the number of offices, turnover per office is equal to 25(what you charge) minus 4(what the supplies cost), you should make a total of 315):
(25-4)*x = 315 -> x=15 offices to break even
2)
The answer is:(x is the current speed)(When we calculate this speed we need to do 2(against current) + current speed. This should be equal to 3 minus the current speed for the return), so:
2+x = 3-x -> x=0.5 miles per hour

314=(25-4)x
solve for x

if rita's paddle speed is x, and the current speed is c, than you can solve two equations to get both variables:
upriver, x-c=2
downriver, x+c=3

solving, x=2+C -> (2+c)+c=3 -> 2c=1, c=.5mi/h
x-.5=2, x=2.5mi/h

Rita paddles at 2.5mi/h, the current is .5mi/h