12. Xiaoli and Xiaoying both have some comic books. If Xiaoying gives Xiaoli 7 comic books, Xiaoli's number of comic books will be 5 times that of Xiaoying. If Xiaoli gives Xiaoying 9 comic books, Xiaoli's number of comic books will be 3 times that of Xiaoying. Originally, Xiaoying had ( ) comic books, and Xiaoli had $(\quad)$ comic books.
【Answer】 $39 \quad 153$
【Analysis】Suppose Xiao Ying originally had $(x+7)$ books, then Xiao Li had $(5x-7)$ books. According to the problem, we have: $3(x+7+9)=5x-7-9$, solving this gives $x=32$. Therefore, Xiao Ying originally had 39 books, and Xiao Li had 153 books.
【Lecture Comparison】Application of Difference and Multiple Problems Short-term Class Lecture 1