ANSWER
A = 90 cm²
Step-by-step explanation
This is the rectangle
The perimeter of a rectangle is:
We know the perimeter is 42cm and the width is 6cm, we can find the length:
![\begin{gathered} 42=2\cdot6+2L \\ 42=12+2L \\ 42-12=2L \\ L=(42-12)/(2) \\ L=(30)/(2) \\ L=15\operatorname{cm} \end{gathered}]()
The area of a rectangle is:
Now that we've found the length we can find the area:
![A=6\operatorname{cm}*15\operatorname{cm}=90\operatorname{cm}^2]()