Question 410561
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Hi
Let x and (x+20mph)represent their respective speeds.  t = D/r
Question states***
  330/x + 330/(x+20) = 3hr
Solving for x
 330(x+20) + 330x = 3x(x+20)
  660x + 6600 = 3x^2 + 60x
   3x^2 -600x - 6600 = 0
  3(x^2 - 200x - 2200) = 0
{{{x = (200 +- sqrt( 48800 ))/(2) }}}
  x = 210.4536   |negative solution tossed out for speed
CHECKING our Answer***
  330/210 + 330/230 = 3hr  |to the nearest whole number