Consider a series of $115 end-of-period CFs spanning 2053-2057 and a $121 CF at the end of 2042. The interest rate is 1.5%. What is the equivalent value of these CFs at the end of 2047? (answer: $640.90)

Consider a series of $123 end-of-period CFs spanning 2053-2057 and a $143 CF at the end of 2066. The interest rate is 2.2%. What is the equivalent value of these CFs at the end of 2061? (answer: $829.37)

What formulas are used and please show steps as i already hav ethe answer but need to know how to do this on paper not excel

thank you