Question

Patrick drank 0.75 liter of water Monday before jogging.he drank 0.8liter of water after his jog.

Answer 1

if you want to find out how much he drank in total, its simple. Just add 0.75 and 0.8

  ¹0.75 Liters
+ 0.8   Liters
---------
   1.55  Liters
(make sure to add the units AKA: liters)

Therefore, 
Patrick drank 1.55 Liters of water in total. 

Hope this helps and have a great day :)