Final answer:
The day after Friday that will be a holiday after 72 days will be Tuesday.
Step-by-step explanation:
If every 4 days in Abuja is a holiday, to find out which day will be a holiday after 72 days, we can divide 72 by 4. Since 72 divided by 4 is 18, we know that there will be 18 holidays in the 72 days. Now we need to determine the day of the week of the last holiday (Friday) and count 18 days from there to find the next holiday. Since there are 7 days in a week, 18 days later would be 4 (18 divided by 7 gives a remainder of 4) days after Friday. Therefore, the day after Friday that will be a holiday after 72 days will be Tuesday.