The problem says that every color of bookcases is avaiable in every size, and the furniture manufacturer offers 3 sizes and 4 differents colors. So, to calculate the total number of different bookcases, we must multiply the number of different color offered and the sizes avaibles. Then:
x= axb
x: the total number of different bookcases.
a: the number of different color offered.
b: the number of the sizes avaibles.
x=4x3
x=20
Then, the total number of different bookcases is: 20 bookcases.
