Question 1010851
Simple interest: A= C(1+r). Now to your problem:
Solve for x:
1.05x-3150+0.05(1.05x-3150) = 4400 Let's simplify, eliminate the parenthesis:
0.05(1.05x-3150) = 0.0525x-157.5 OK, back to the equation but let's group like terms: 
(1.05x+0.0525x)+(-3150-157.5) = 4400 Now add/subtract in this equation and you get:
1.1025x-3307.5 = 4400 Add 3307.05 on both sides:
1.1025x= 7707.05 Divide both sides by 1.1025:
x= 6,990.52 is the original amount the man borrowed.
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Check:
6990.52(1+0.05)= 6990.52*1.05= 7340.05 This is what the man owes at the end of the first year. At that point he pays 3150:
7340.05-3150= 4190.05 So we go into the second year:
4190.05*1.05= 4400 is the final payment on the debt. We have the correct answer (I get 43999.55 and it's because of the rounding of numbers)