Question 716491
Your proportion should always have the units in the same place in both terms for example in this situation: miles/time = miles/time
 Plug in what you know from the word problem:

25miles/1hour = 50miles/'x'hours
CROSS MULTIPLY
25x=50
Divide both sides by 25 to get x alone
x=2

Don't forget the units that the question is asking for. 2 hours