Question 980634
We know that when they work together, they can complete the lawn job in 1 hour and 10 min, which is the same as 7/6 of an hour (1 hour and 10 min = 70 minutes.  70 minutes/60 minutes = 7/6).  We normally are asked to find out how long it would take 2 people to do 1 job if each works at a certain rate.  For instance, if our question said, "It takes John 3 hours to mow the lawn and it takes Suzy 4 hours to mow the lawn, how long would it take them to work together?"  We would set the equation up as follows:


{{{(x/3)+(x/4)=1}}}


In our case, we already know how long it takes them to work together (7/6 hours), but we don't know how long it takes Craig to mow the lawn working alone.  So, where the x's are in our normal equation, we would put 7/6 in it's place.  In the denominator of the fraction representing Craig, we would list an x, so the equation would look like the following:


{{{((7/6)/2)+((7/6)/x)=1}}}


Now we would solve for x.  


First, we can multiply our equation by the LCD of our fractions, which is 2x.  Multiplying our entire equation by 2x would give us:


{{{((7x)/6)+(14/6)=2x}}}


Next, multiply our equation by 6 to get rid of all of our fractions.  This will give us:


{{{7x+14=12x}}}


Subtract 7x from both sides, which will give us:


{{{14 = 12x -7x}}} -----> {{{14=5x}}}


Divide both sides of the equation by 5, which will give us:


{{{14/5=x}}} ----->{{{2.8=x}}}


It will take Craig 2.8 hours to mow the lawn when working alone.  To convert 2.8 hours to hours and minutes, just multiply 60 by .8:


{{{60*.8=48}}}


So, it will take Craig 2 hours and 48 minutes to mow the lawn when working alone.


ANSWER:  2 hrs 48 min