Question 397197
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Hi
Let x represent the speed of the plane
Questions states***   (D = r*t  OR r = D/t
  x + 30 =  D/5
  x - 30 =  D/7
 2x = (12/35) D
  x = (6/35)D
 
  x + 30 =  D /5
(6/35)D + 30 =  D/5
       30 = (1/35)D
      30*35 = D
      1050mi  = D
              x = (6/35)1050 = 180mph

CHECKING our Answer
  150 = 1050/7