Formula and method
Each month, add interest, pay the entered fixed minimum on each debt, then send the remaining fixed budget to the priority balance. The highest-rate method prioritizes APR; the snowball method prioritizes the smallest remaining balance. Once a debt clears, keep its payment in the total budget.
Worked example
Two zero-interest debts of $1,000 and $500 with $100 and $50 minimums plus $150 extra use a $300 monthly budget. Both strategies clear the $1,500 total in five months.