Please, do not use excel for calculations but rather an equation that explains everything. please do not use for example ( Rate ( 925,30,20,1000)...)

I need to be able to understand it and calculate on my own without excel. Thank you

1. Brien Ltd.'s outstanding bonds have a $1,000 par value, and they mature in 25 years. Their nominal annual, not semiannual yield to maturity is 9.25%, they pay interest semiannually, and they sell at a price of $875. What is the bond's nominal coupon interest rate