Question 1159415
B+R+L=4000
9B+6R+4L=25240
4.5B+3R+4L=15760, since half the seats of one type is half the money, even if the number is unknown.
multiply the last by -2 and add to the second
-9B-6R-8L=-31520
-4L=-6280
L=1570 lawn seats or $6280 revenue
B+R=2430
9B+6R+6280=25240 or
9B+6R=18960, multiply the B+R equation by -6 and add
-6B-6R=-14580
3B=4380
B=1460  box seats or $13140 if all sold
R=2430-1460=970 reserved seats or $5820 if all sold 

(B, R, L)=(1460, 970, 1570)