Both rectangles need to be divided into a number of of parts that is divisible into both 3 and 4 parts. Since 3 and 4 don't have any factors in common, it has to be divisible by both 3 and 4, so it has to have minimally 3*4=12 parts (answer to A and B!) but it can be any multiplication of 12, such as 24, 36, etc.