Answer: 12.32%
Explanation:
1.
is the original long side and
is the original short side.
2. The area of the original rectangle is
.
3. The rectangle is extended 4% on the long sides and 8% on the short sides. therefore, the new long side is:
![(104)/(100)x=(26)/(25)x](https://img.qammunity.org/2019/formulas/mathematics/middle-school/wnn6mitle4uoywjpy9ts47n5vxc3ylio8z.png)
4. And the new short side is:
![(108)/(100)y=(27)/(25)y](https://img.qammunity.org/2019/formulas/mathematics/middle-school/f6q0ov0sdxyt3veekriqxc9cathzqs2v1f.png)
5. The new area is:
![((26)/(25)x)((27)/(25)y)=(702)/(625)xy](https://img.qammunity.org/2019/formulas/mathematics/middle-school/qdrkjwsjafi330c7px26suy3ysxbm587hr.png)
6. The percentage of increase is calculated by substracting the new area and the original area:
![(702)/(625)xy-xy=0.1232xy](https://img.qammunity.org/2019/formulas/mathematics/middle-school/a945hgnhd5qbemi72dqmwvr371wd8t0xrh.png)
7. The result is:
(0.1232)(100)=12.32%