What is the monthly payment for a $20,230 loan at 11.5 percent for 20 years?

The main formula is

M = P (i (1+i) ^n) / (1+i) ^n) - 1

M: monthly payment

P: mortgage principale = $20,230

i=montly interest, 11.5%=11.5/100=0.115, i = 0.115/12=0.009

n=number of months=12x20 (years) = 240 months

M = $20,230 (0.009 (1.009) ^240) / (1.009) ^240-1 = $20,230 x 0.0077 / 8.58-1

M=$20.57