Find how much times blood is filtered in the kidney?
I'll try to dissect your teachers answer for you:


  1/12*60=5 liter blood


no explanation required here


  0.55*5=2.75 liter plasma of blood.


only the plasma is filtered in the kidney (the 45% cell content remains in the blood stream), so out of the 5 l blood, only 2.75 l need to be filtered.


  The plasma is filtered 60 times is 24 hours. (how did she find that?)


the kidney filteres 7.5 l per hour so if the whole blood plasma has 2.75 l, then in one hour the whole blood is filtered 7.5/2.75=2.73 times. In one day the whole blood is filtered 2.73*24=65.5 times (the numbers are slightly rounded).