Answer:
z=7.9 cm
Explanation:
So, what we have to do is gather all the information we already have. The length of the rectangle is 20.4 cm, and the perimeter is 56.6. To find the perimeter, you always add all the sides up. So 20.4+20.4 is 40.8. since 4+4 is 8, and 20+20 is 40. Then, you subtract that from the perimeter to get what is 2z(both sides). 56.6-40.8 is 15.8. So we know 2z is 15.8. To find z, we divide 15.8 by 2 which is 7.9. You can do this with a calculator or write it down.
z=7.9 cm