20. Reggie can paint a house in 5 hours. Fernando can paint the same house in 6 hours while Mark can do the same job in 3 hours. First, Reggie and Fernando start working together for 2 hours. Then Mark

finished the job alone. How long did it take mark to finish?

rate

time

Total work done

Reggie

Fernando

Mark

24. In a river that flows at 4km/h, a boat takes twice as long to travel 40km upstream as it does to travel

32km downstream At what rate does the boat travel in still water?

Rate

Distance

Time

upstream

downstream

{x = -1/2 ,   y = -1

step-by-step explanation:

solve the following system:

{2 x + y = -2

{10 x - 3 y = -2

in the first equation, look to solve for y:

{2 x + y = -2

{10 x - 3 y = -2

subtract 2 x from both sides:

{y = -2 x - 2

{10 x - 3 y = -2

substitute y = -2 x - 2 into the second equation:

{y = -2 x - 2

{10 x - 3 (-2 x - 2) = -2

10 x - 3 (-2 x - 2) = (6 x + 6) + 10 x = 16 x + 6:

{y = -2 x - 2

{16 x + 6 = -2

in the second equation, look to solve for x:

{y = -2 x - 2

{16 x + 6 = -2

subtract 6 from both sides:

{y = -2 x - 2

{16 x = -8

divide both sides by 16:

{y = -2 x - 2

{x = -1/2

substitute x = -1/2 into the first equation:

{y = -1

{x = -1/2

collect results in alphabetical order:

answer:   {x = -1/2 ,   y = -1

to find the total number of combinations, multiply the quantity of each item by each other:

2 pairs of shoes x 3 pairs of shorts = 6 different combinations.