Important question guys

[Andrea Salvati]

Hey guys! 

I was reading John W. Shaub's "Building Wealth One House at a Time" and I got stuck with two maths questions. Does anybody know how to solve it? How did he determine the interest rate? and in the second one, how did he determine the amount of the loan? 

I'll be grateful if you guys can help me as I believe this topic is very important. 

By the way, a must-read book!!