<PRE><B>Question 163444</B>
Let x represent the number of hours, so after x hours the distance between Dallas and private jet is twice the distance between Dallas and commercial plane.

Then {{{x/3}}} represents the portion of distance traveled by commercial airplane after x hours,  {{{1- x/3}}} represents the portion of total distance from Dallas to commercial air plane.

In the same way, {{{1 - x/3.5}}} represent the portion of total distance between Dallas and private jet.

So we have the equation:

{{{2*(1- x/3)}}} = {{{1 - x/3.5}}}

solve it:

{{{2 - (2x)/3}}} = {{{1 - x/3.5}}}

simplify:

1 = {{{(2x)/3}}} - {{{x/3.5}}}

1 = {{{((2x*3.5)-(3*x))/(3*3.5)}}}

1 = {{{4x/10.5}}}

x = 10.5/4 = 2.625 hrs

The answer is 2.625 hours, or {{{2 5/6}}} hours</PRE>