Question 263123
This is a working together or job / time problem.
 We are given 
Sally's rate = 1/4
Steve's rate = 1/6
together time = x total jobs = 1
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we use the following equation:
{{{(J1/T1)*x + (J2/T2)*x = Tj}}}
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from above we get
{{{(1/4)x+(1/6)x = 1}}}
multiply by 12 to get
{{{3x + 2x = 12}}}
solve for x as
{{{5x = 12}}}
and then
{{{x = 12/5}}}
or 2.4 hours.