Calculate the value, A, of the original loan.
A = 20000*(1 + 0.06/12)⁶⁰ = $26,977.00
Calculate the monthly payment
p = 26977/60 = $449.62
After 32 payments, the remaining value of the loan is
26977 - 32*449.62 = $12,589.27
The number of remaining payments is 60-32 = 28.
If x = the outstanding principal balance, then
x*(1 + 0.06/12)²⁸ = 12589.27
1.15x = 12.589.27
x = 10947.19
Answer: The outstanding principal balance is $10,947.19