Answer:
Step-by-step explanation:
No need for complicated formulas if you only need the number of months/payments.
Ignore the APR as it won't make such a great amount to add a month payment within short period up to 6 months.
a.
You are paying at the beginning of the month.
After the first payment you have a balance:
This amount will be paid off after 5 months as:
So total number of months/payments is 6
b.
Similarly to above, after the first payment the balance is:
This amount will be paid off after 2 months as:
Total number of months/payments is 3.