Question 314417
Let x = time it takes them to mow the yard working together.  This means that in 1 hour, Jack can mow 1/3 of the yard, Jane can mow 1/4 of the yard, and working together, they can do 1/x of the yard.


The equation is
{{{1/3+1/4=1/x}}}


The LCD is 12x, so multiply both sides of the equation by 12x
{{{12x*(1/3)+12x*(1/4)=12x*(1/x)}}}
{{{4x+3x=12}}}
{{{7x=12}}}
{{{x=12/7}}} hours (a little less than 2 hours working together.


Dr. Robert J. Rapalje, Retired
Seminole State College of Florida
Altamonte Springs Campus