7.2. Person A and Person B perform division with remainder on the same number. A divides it by 8, and B divides it by 9. It is known that the sum of the quotient obtained by A and the remainder obtained by B equals 13. Try to find the remainder obtained by A.


7.2. Let $a$ and $b$ represent the quotient and remainder obtained by Jia, and let $c$ and $d$ represent the quotient and remainder obtained by Yi. Thus, we have
$$
8 a+b=9 c+d, a+d=13 \text{. }
$$

Substituting $d=13-a$ into the first equation, we get $9(a-c)=$ $13-b$, so $13-b$ is divisible by 9. Since $b$ can only be an integer from $0 \sim 7$, we know that $b=4$.