Question 130738
Let's find the hourly rate of work:
Y = you and C = your cousin.
The two of you can refinish the table in 8 hours, so you both can do 1/8 of th table in one hour. Write this as:
{{{(Y+C)(1) = 1/8}}}
Your cousin alone can refinish the table in 12 hours, so he/she can do 1/12 of the table in one hour. Write this as:
{{{C(1) = 1/12}}}
Now, if you subtract these you can find out how much you can do in one hour.
{{{(Y+C) - C = 1/8 - 1/12}}}  Of course, (Y+C)-C = Y, so...
{{{Y(1) = 1/8 - 1/12}}} 
{{{Y(1) = (3-2)/24}}}
{{{Y(1) = 1/24}}} So, in one hour, you can refinish 1/24 of the table. Multiply both sides by 24 to see how many hours it would take you to refinish the entire table.
{{{Y(24)(1) = (24)(1/24)}}}
{{{24 = 1}
So it would take you 24 hours to refinish the whole table.