Question 148128
You need to break the trip into two parts.
The total trip is 220. The total time is 3 hours.
Let the distance from Albuquerque to Roswell be x (watch out for aliens in Roswell). 
Then the distance from Roswell to Carlsbad is {{{220 -x}}}  

The time for each leg is given by {{{distance/speed = time}}}
The time to Roswell is {{{x/75}}}
The time to Carlsbad is {{{(220-x)/70}}}
The total time is 3 hours.

{{{3 = x/75 + (220-x)/70}}}
{{{3 = x/75 + 220/70 - x/70}}}
{{{3 - (200/70) = x/75 - x/70 }}}
{{{((210 - 220)/70) = (70x - 75x)/(70*75) }}}
{{{((70*75)*(-10/70)) = - 5x}}}
{{{-750 = -5x}}}
{{{150 = x}}}
So the distance to Roswell is 150 miles.

At an average speed of 75 mph, the drive to roswell takes 2 hours.