Final answer:
The maturity date of the note will be October 31st.
Step-by-step explanation:
The maturity date of a note can be calculated by adding the number of days to the issue date. In this case, Mr. Robert signed a 120-day note on August 5th. To find the maturity date, we add 120 days to August 5th.
August has 31 days, so we have 120 - 31 = 89 days remaining.
September has 30 days, so we have 89 - 30 = 59 days remaining.
October has 31 days, so we have 59 - 31 = 28 days remaining.
November has 30 days, so we have 28 - 30 = -2 days remaining.
Since we have a negative number of days remaining in November, we go back one day to October 31st. Therefore, the maturity date of the note is October 31st.