Question 290191
First, make a table for the given terms:


Let's say airplane A is the one that flies for 400mph and airplane B that flies for 250mph. Since what we are looking for is "how many hours", the column for Time for both A & B will be left unknown and it was because there was no time given on either of the two airplanes. The unknown time will be represented by (t).

Remember these formulas back from your physics (don't worry about physics stuff on this algebra matter. just recall these formulas to help you solve with this kind of question): 


Distance = rate x time


v = s/t      v = stands for velocity or rate ; s = stands for speed or distance

                            
s = vt

_______________________________________________________________________________
  Airplane    |     Rate     |     Time    |   Distance (rate x time)
________________________________________________________________________________
    A         |    400mph    |       t     |         400(t)
________________________________________________________________________________
    B         |    250mph    |       t     |         250(t)
________________________________________________________________________________
   Total                                   |         1625 miles
________________________________________________________________________________



Remember to create a table for this kind of question so we could easily identify which is which and accord it to a linear equation.


Then, apply linear equation.

                 
                     400(t)  +   250(t)  =  1625 miles

                                 650t    =  1625


                                 650t    = 1625
                                 ____      _____

                                 650        650


                                     t = 2.5   --------> your answer match.
                                                          so let's check



                        checking:

                      just substitute the (t)


                       400(2.5) + 250(2.5) = 1625
                   
                         1000   +   625    = 1625
 
                                     1625  =  1625     ----> correct!



I hope this helps. This is the first question here that i answered. Goodluck!