When you see the 1/2 of any number, actually you'are been asked about the half of that number.
• What is the 1/2 or the half of 10? Answer = 5
,
• What is the 1/2 or the half of 444? Answer = 222
For odd numbers, it's not an integer, it is decimal.
• What is the 1/2 or the half of 77? Answer = 38.5
,
• What is the 1/2 of the half of 885? Answer = 442.5
Now, with all this information, you can easily calculate the 1/2 or half of 80.