13. Person A and Person B use the same amount of money to buy the same type of candy, A buys the ones in tin boxes, and B buys the ones in paper boxes. Both try to buy as much as possible, and as a result, A buys 4 fewer boxes than B and has 6 yuan left, while B uses up all the money they brought. If A uses three times the original amount of money to buy the tin-boxed candies, they would buy 31 more boxes than B and still have 6 yuan left. Therefore, the price of the tin-boxed candies is $\qquad$ yuan per box, and the price of the paper-boxed candies is $\qquad$ yuan per box.
【Answer】 12 yuan, 10 yuan
【Key Points】Divisors and Multiples, Solving Application Problems with Equations
【Analysis】
If A uses the original money to buy iron boxes and has 6 yuan left, then using 3 times the money to buy iron boxes theoretically should leave $6 \times 3=18$ yuan, but still leaves 6 yuan, which means $18-6=12$ yuan can exactly buy several iron boxes, i.e., the unit price of the iron box should be a divisor of 12; and according to the 6 yuan left, the unit price of the iron box must be greater than 6 yuan, so the unit price of the iron box can only be 12 yuan per box; let B buy $x$ paper boxes, from the relationship of the money used by A twice, we can set up the equation:
$3[12(x-4)+6]=12(x+31)+6$, solving for $x=21$;

So the original amount of money the two had is $12 \times(21-4)+6=210$ yuan, the unit price of the paper box is $210 \div 21=10$ yuan.