Question 165977
lets call
x    the speed of the aircraft the first 3 hours and 
x-75 the speed of the aircraft the final 2 hours.

            so: 3x + 2(x-75) = 1600
            
             distribute the 2nd term
  
              : 3x + 2x-150=1600 combine like terms
              : 5x=1750  {{{x=350}}}
so the rate of first 3 hours was {{{350mph}}}
and the rate of the final 2 is 350-75={{{275mph}}}