Solution: How many books does my brother give my brother? My brother is twice as big as my brother. We can do it by solving equations. Suppose my brother gives my brother X books, my brother's current book is 12-x, and my brother's current book is 12+X, from which we can solve the equation, namely:

Solution: Let the elder brother give the younger brother X books. The younger brother is twice as old as the older brother.

2×( 12-x)= 12+x

24-2x= 12+x

24- 12=x+2x

12=3x

x= 12÷3

x=4

A: My brother gave my brother four books. My brother is twice as big as my brother.