Question 80898
Alexandra and Frank can assemble a swing set working together in 6 hours.  One day, when Frank called in sick, Alexandra was able to assemble a swing set in 10 hours.  How long would it take Frank to assemble a swing set if he worked by himself?
:
Let x = time required for F to assemble by himself
:
Let the completed job = 1
:
{{{6/10}}}+ {{{6/x}}} = 1
:
Multiply equation by 10x to get rid of the denominator:
x(6) + 10(6) = 10x
:
6x + 60 = 10x
:
6x - 10x = -60
:
-4x = -60
:
x = -60/-4
:
x = 15 hrs for F to complete the job
:
:
Check the x = 15 solution:
6/10 + 6/15 =
3/5 + 2/5 = 1