Question 411334
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Hi
D = r*t
Let x represent the submarines speed.
Question states*** 280mi apart after traveling opposite directions
 11hr*x + 25mph*9hr =  280mi   |note:submarine left Hawaii two hours before an aircraft carrier
Solving for x
    11hrx = 55mi
      x = 5mph, the submarine's speed

CHECKING our Answer***
 55mi + 225mi = 280mi