Since the question requires you to give the answer in terms of steps/minute, the first step would be to convert hours to minutes: 12.5 hours = 750 minutes. Next, if he took 775 steps in 750 minutes, how many would he take in 1 minute? This requires you to set up the question as a proportion: (775 steps/ 750 minutes) = (x steps/1 minute)
It isn't easy really but you can always divide the number out. For example 50% of 200 is 100 by dividing 200 by 2 or 25% of 100 is 25 by dividing 100 by 4 since 25% is equivalent to 1/4