Let's sum these two numbers.
9 + 42 = 51 total hours.
In every 12-hour the clock format changes AM to PM or the opposite PM to AM. So we need to divide 12 with the result 51.
There are 4 times 12 number in the 51
If the result is ODD number the time format will change the opposite side. If the result is EVEN number the time format will be the same.
Answer :3pm
What is 42 hours from 9pm ? = 3pm.
Add 42 hours to 9pm is equal 3pm.