How did they get those answers?

QUESTION 5 5.1. What amount of money must be invested now so as to accumulate to R1751 in 17 mohths time at 12% pa compound interest. Answer: R1478.50 5.2. A couple, who are both working, invest R160 a month each in a joint savings account which carries interest of 20% pa compounded monthly. After 3 years the interest rate drops to 13 percent and the couple continue paying into the account for a further year. How much money will be in the account at the end of this period? Assume that no withdrawals were made. Answer: R21844.35