It's a simple linear equation in a single variable, 'y' . Its solution is the number
that 'y' must be in order to make the equation a true statement. Here's how to
find the solution:
Write the equation: <span>15 = -y + 10
Subtract 10 from each side: 5 = -y
Multiply each side by -1 : <u>-5 = y</u>
</span>
so two fellows did all the carpeting in 10 days.
now, how long did "1" fellow work only? well, it worked for 10 days.
how long did the other fellow work for? well, it was working alongside the first one, and it was there for also 10 days.
so the two guys working together, really did 10+10 = 20 "days worth of work". So that the whole carpeting job can be done in 20 "days worth of work".
now if we want to finish it in 4 days, 20 ÷ 4 = 5.
so if we hire 5 guys, since each one will do 4 days worth, 5*4 = 20 <- the whole job.
You can factor out a 5n to get
5n(4m-3)
