For your interest problem
The answer is not too difficult if you go back to the basic formula for interest: A=P(1+r)^t. She had her money in for 10 years at 10% so it would be 10,000= x(1+.1)^10 therefore 10'000/(1.1^10)=x. Now you go back to the guy and he has had his money in for 12 years. Therefore A=(x~3855.43)(1.1)^12 which equals your answer. I left my TI-89 in the car but I did it the hard way on a cheap calculator with no functions to check it out and I was within a few cents of your answer which would be due to rounding on the cheap tools I had available to me.
I hope this helped.