Atheater holds 2,680 seats. the lower level has 100 less than 2 times as many seats as the upper level. the middle level has 80 more than 3 times as many seats as the upper leveel. how many seats are in the middle level?

x + y + z = 2680 
x = 2z - 100 
y = 3z + 80 
x + y = 5z - 20 
6z - 20 = 2680 
z = 450 
y = 1430 
Solution: 
x = 800, y = 1430, z = 450 
The middle level has 1430 seats. 
 

step by step solution :

step   1   :

1.1     4 = 22

(4)3 = (22)3 = 26

equation at the end of step   1   :

  ((23) • 26)2

step   2   :

equation at the end of step   2   :

  (23 • 26)2

step   3   :

final result :

  218

ya

i honestly dont know