Firstly in this question, we convert the time given to minutes.
Using the conversion of 60 seconds make a minute, we have 3/4 hours as 3/4 * 60 = 45 minutes. Let’s add this to a total of 3 hours which is 180 minutes. This gives a total of 225 minutes.
Now, we are told that he spends 2/5 of his time lifting weight. This is equivalent to 2/5 * 225 = 90 minutes