Answer:
(4x+z)=13000------1
(4x+z)13000=503000----2
Explanation:
let x be the number of seats in A,
y be the number of seats in B, and
z be the number of lawn seats.
y=3x
the total number of seats is given by
(x+y+z)=13000
put y=3x
(x+3x+z)=13000
(4x+z)=13000------1
also
(4x+z)13000=503000----2
hence the systems of equation is
(4x+z)=13000------1
(4x+z)13000=503000----2