Answer :

Hello, 

We know that th formula for the area of a rectangle is: [tex]A=b*h[/tex]
Now, the problem in this excercise is that there is no restriction on the values that b and h can take, so, they can take any value provided that it meets:  [tex]b*h=12 cm^{2} [/tex]
for example:
[tex]lenght= \frac{12}{3}cm \,\,\,\,\,\,and\,\,\,\,width= 3 cm \\ \\ A=\frac{12}{3}cm*3cm \\ A=12 cm^{2} [/tex]

But if they can only take intenger values, what we have to do is to descompose 12, and then we can analyze the possible solutions.

12   |  2
  6   |  2
  3   |  3
  1

12= 2 *2*3

first option:
12=4*3

Answer: lenght= 4cm   and   width= 3cm  or vice versa

second option:
12=2*6

Answer: lenght= 6cm   and   width= 2cm  or vice versa